- What is Kidney Stone
- Special Considerations
- What is the urinary tract and how does it work ?
- What types of kidney stones are there ?
- Table 2. Composition of Kidney Stones
- What Causes Kidney Stone
- Anatomical abnormalities that increase the risk of kidney stone disease
- Medications Associated with Kidney Stone Formation
- Does Obesity Increase Risk and Will Weight Loss Reduce Your Risk for Kidney Stones ?
- Should people with a history of kidney stones reduce their fructose intake ?
- Struvite (triple phosphate) and cystine stones
- Urinary glycoproteins
- Drugs that may increase the risk of stone disease
- What are the disordered physiological processes associated with Kidney Stone
- What are the complications of kidney stones ?
- What are Symptoms and Signs of Kidney Stone
- How Kidney Stone is Diagnosed
- How To Treat Kidney Stone
- How To Prevent Getting a Kidney Stone
- For prevention of calcium oxalate, cystine, and uric acid stones, urine should be alkalinized
- For prevention of calcium phosphate and struvite stones, urine should be acidified
- Can Bacterial Infection Trigger Recurrence ?
- Specific treatments to prevent recurrent stones
- What is Renal Tubular Acidosis
- How is Renal tubular acidosis diagnosed ?
- What are the types of renal tubular acidosis ?
- Table 5. Features of Different Types of Renal Tubular Acidosis
- What is Fanconi’s syndrome
- What is Cystinuria
- What is Urinary Tract Infections
- Bacterial Urinary Tract Infections
- The disordered physiological processes associated with Bacterial Urinary Tract Infections
- Risk factors for Bacterial Urinary Tract Infections
- Causes of Bacterial Urinary Tract Infections
- Classification of Bacterial Urinary Tract Infections
- Symptoms and Signs of Bacterial Urinary Tract Infections
- Diagnosis of Bacterial Urinary Tract Infections
- Treatment of Bacterial Urinary Tract Infections
- Prevention of Bacterial Urinary Tract Infections
- What are Cystic Kidney diseases
- What are the differences between acquired cystic kidney disease and polycystic kidney disease ?
- What is Polycystic Kidney Disease ?
- What causes Polycystic kidney disease ?
- Inheritance Pattern and Genetic Changes of Polycystic kidney disease
- How common is Polycystic kidney disease ?
- Who is more likely to have Polycystic kidney disease ?
- What are the signs and symptoms of Polycystic kidney disease ?
- Diagnosis of Polycystic kidney disease
- Can you prevent polycystic kidney disease ?
- What can you do to slow down polycystic kidney disease ?
- Make lifestyle changes To Slow Down Polycystic Kidney Disease
- Treatment of polycystic kidney disease
- Outlook (Prognosis) for polycystic kidney disease
- Possible Complications of polycystic kidney disease
- What is acquired cystic kidney disease ?
- How common is acquired cystic kidney disease ?
- What causes acquired cystic kidney disease ?
- What are the signs and symptoms of acquired cystic kidney disease ?
- What are the complications of acquired cystic kidney disease ?
- How is acquired cystic kidney disease diagnosed ?
- How is acquired cystic kidney disease treated ?
- Eating, Diet, and Nutrition for Acquired Cystic Kidney Disease
- Nutrition for Advanced Chronic Kidney Disease in Adults
- What is medical nutrition therapy (MNT) ?
- Why is knowing about calories important for someone with advanced chronic kidney disease ?
- Why is knowing about protein important for someone with advanced chronic kidney disease ?
- What is the right meat portion size ?
- Why is knowing about fat important for someone with advanced chronic kidney disease ?
- Why is knowing about sodium important for someone with advanced chronic kidney disease ?
- Why is knowing about potassium important for someone with advanced chronic kidney disease ?
- Why is knowing about phosphorus important for someone with advanced chronic kidney disease ?
- Why is regulating fluid intake important for someone with advanced chronic kidney disease ?
- Is there kidney stone home remedy
- Does the type of kidney stone you have affect food choices you should make ?
What is Kidney Stone
Kidney stones affect up to 5% of the population, with a lifetime risk of passing a kidney stone of about 8-10% 1). About 1/1000 adults in the US is hospitalized annually because of kidney stones, which are also found in about 1% of all autopsies 2). Up to 12% of men and 6% of women will develop a urinary calculus by age 70 3). Increased incidence of kidney stones in the industrialised world is associated with improved standards of living and is strongly associated with race or ethnicity and region of residence 4). A seasonal variation is also seen, with high urinary calcium oxalate saturation in men during summer and in women during early winter 5). Men are more likely to develop kidney stones than women and kidney stones form twice as often in men as women 6). The peak age in men is 30 years; women have a bimodal age distribution, with peaks at 35 and 55 years 7). Once a kidney stone forms, the probability that a second stone will form within five to seven years is approximately 50% 8). In postmenopausal women, the occurrence of kidney stones is associated with a history of hypertension and a low dietary intake of magnesium and calcium 9).
Kidney stones vary in size and shape. Kidney stones vary from small as a grain of sand or as large as a pea to kidney stones several centimeters in diameter. Rarely, some kidney stones are as big as golf balls. A large kidney stone, called a staghorn calculus, can fill an entire renal calyceal system.
Kidney stones may be smooth or jagged and are usually yellow or brown. Most ureteral stones under 5 mm pass spontaneously 10). About 90% of ureteric stones smaller than 5 mm pass spontaneously, compared with about 50% of stones between 5 mm and 10 mm, so conservative management is preferred for ureteric stones 11). Depending on the size of the stone, the average time to pass the stone ranges between one week and three weeks, and the passage of the stone is most accurately assessed by a plain film (kidney-ureter–bladder view) every one to two weeks to monitor progression. An observation period of three to four weeks is reasonable unless urgent intervention is indicated for intractable symptoms, infection, or obstruction 12).
A small kidney stone may pass through your urinary tract on its own, causing little or no pain. A larger kidney stone may get stuck along the way. A kidney stone that gets stuck can block your flow of urine, causing severe pain or bleeding.
If you have symptoms of kidney stones, including severe pain or bleeding, seek care right away. A doctor, such as a urologist, can treat any pain and prevent further problems, such as a urinary tract infection (UTI).
More children are developing kidney stones, which is attributed to the corresponding rise in diabetes, obesity, and hypertension in this population 13), 14). Because increasing age is a risk factor for kidney stones, adolescents are more likely to form stones than younger children. The underlying causes and resulting treatments differ in children and adults. Children with kidney stones are more likely to have anatomic and metabolic abnormalities 15), increased urinary calcium excretion, decreased urinary oxalate and citrate excretion, and much higher urinary calcium oxalate saturations than children with no history of kidney stones 16). Children with cystinuria and other hereditary forms of kidney stones are at increased risk of decline in renal function compared with age-matched controls, although progression to end-stage renal disease is uncommon 17).
Pregnant women are twice as likely to have calcium phosphate stones compared with age-matched nonpregnant women, and are two to three times more likely to have calcium phosphate stones than oxalate stones 18). The incidence of kidney stones during pregnancy increases in the second and third trimesters. Women have an increased glomerular filtration rate and higher urinary calcium excretion throughout pregnancy, with higher urine pH in the second and third trimesters, which may predispose them to calcium phosphate stones. Ultrasonography is considered the imaging modality of choice in pregnant women. Kidney stones during pregnancy increase the risk of urinary tract infections, and pregnant women with renal colic have nearly double the risk of pre-term delivery compared with women who do not have kidney stones 19).
What is the urinary tract and how does it work ?
The urinary tract is the body’s drainage system for removing urine, which is composed of wastes and extra fluid. In order for normal urination to occur, all body parts in the urinary tract need to work together in the correct order 20).
- The urinary tract is the body’s drainage system for removing urine, which is composed of wastes and extra fluid.
- The urinary tract is important because it filters wastes and extra fluid from the bloodstream and removes them from the body.
- In order for normal urination to occur, all body parts in the urinary tract need to work together in the correct order.
- The kidneys are two bean-shaped organs, each about the size of a fist.
- Every day, the kidneys filter about 120 to 150 quarts (114 liters – 142 liters) of blood to produce about 1 to 2 quarts (950 ml – 1.9 liter) of urine.
- Ureters are the thin tubes of muscle—one on each side of the bladder—that carry urine from each of the kidneys to the bladder.
- The bladder, located in the pelvis between the pelvic bones, is a hollow, muscular, balloon-shaped organ that expands as it fills with urine.
- Bladder emptying is known as urination.
- During urination, the bladder empties through the urethra, located at the bottom of the bladder.
- The ureters, bladder, and urethra move urine from the kidneys and store it until releasing it from the body.
- The amount of urine a person produces depends on many factors, such as the amounts of liquid and food a person consumes and the amount of fluid lost through sweat and breathing.
Kidneys. The kidneys are two bean-shaped organs, each about the size of a fist. They are located just below the rib cage, one on each side of the spine. Every day, the kidneys filter about 120 to 150 quarts (114 liters- 142 liters) of blood to produce about 1 to 2 quarts (950 ml – 1.90 liter) of urine. The kidneys work around the clock; a person does not control what they do. The kidneys remove wastes and extra water from the blood and make urine. To keep the body working properly, the kidneys balance the salts and minerals—such as calcium, phosphorus, sodium, and potassium—that circulate in the blood. The kidneys also release hormones that help make red blood cells, regulate blood pressure, and keep bones strong.
Ureters. Ureters are the thin tubes of muscle—one on each side of the bladder—that carry urine from each of the kidneys to the bladder.
Bladder. The bladder, located in the pelvis between the pelvic bones, is a hollow, muscular, balloon-shaped organ that expands as it fills with urine. Although a person does not control kidney function, a person does control when the bladder empties. Bladder emptying is known as urination. The bladder stores urine until the person finds an appropriate time and place to urinate. A normal bladder acts like a reservoir and can hold 1.5 to 2 cups (325 ml – 470 ml) of urine. How often a person needs to urinate depends on how quickly the kidneys produce the urine that fills the bladder. The muscles of the bladder wall remain relaxed while the bladder fills with urine. As the bladder fills to capacity, signals sent to the brain tell a person to find a toilet soon. During urination, the bladder empties through the urethra, located at the bottom of the bladder.
Three sets of muscles work together like a dam, keeping urine in the bladder between trips to the bathroom.
The first set is the muscles of the urethra itself. The area where the urethra joins the bladder is the bladder neck. The bladder neck, composed of the second set of muscles known as the internal sphincter, helps urine stay in the bladder. The third set of muscles is the pelvic floor muscles, also referred to as the external sphincter, which surround and support the urethra.
To urinate, the brain signals the muscular bladder wall to tighten, squeezing urine out of the bladder. At the same time, the brain signals the sphincters to relax. As the sphincters relax, urine exits the bladder through the urethra.
Figure 1. The Urinary Tract
Figure 2. Normal Kidney Anatomy
Why is the urinary tract important ?
The urinary tract is important because it filters wastes and extra fluid from the bloodstream and removes them from the body. Normal, functioning kidneys
- prevent the buildup of wastes and extra fluid in the body
- keep levels of electrolytes, such as potassium and phosphate, stable
- make hormones that help regulate blood pressure
- make red blood cells
- keep bones strong.
The ureters, bladder, and urethra move urine from the kidneys and store it until releasing it from the body.
What affects the amount of urine a person produces ?
The amount of urine a person produces depends on many factors, such as the amounts of liquid and food a person consumes and the amount of fluid lost through sweat and breathing. Certain medications, medical conditions, and types of food can also affect the amount of urine produced. Children produce less urine than adults; the amount produced depends on their age.
What types of kidney stones are there ?
There are four main types of kidney stones. About 85% of kidney stones in the US are composed of calcium, mainly calcium oxalate (see Table 1: Composition of Kidney Stones); 10% are uric acid; 2% are cystine; most of the remainder are magnesium ammonium phosphate (struvite).
Treatment for kidney stones usually depends on their size, location, and what they are made of 21).
The prevalence of kidney stones (nephrolithiasis) is increasing in women and with increasing age. Table 1 includes rates of different types of kidney stones in children and adults 22), 23). Contributing risk factors for kidney stones are obesity, insulin resistance, gastrointestinal pathology, living in warmer climates, and certain dietary patterns and medications 24), 25).
Table 1. Incidence of Kidney Stones in Children and Adults
|Type||Children (%)||Adult (%)|
45 to 65
56 to 61
24 to 30
8 to 18*
5 to 8
7 to 13
2 to 4
2 to 4
9 to 17
*—Incidence is as high as 75 percent in pregnant women
Calcium stones, including calcium oxalate stones and calcium phosphate stones, are the most common types of kidney stones. Calcium oxalate stones are more common than calcium phosphate stones.
Most patients (up to 80%) with calcium stones have one or more of the metabolic risk factors and about 25% of stones are idiopathic (cause is unknown) in origin.
Metabolic risk factors for calcium stones:
- Hypercalciuria (40-60%)
- Hyperuricosuria (25%)
- Other (vitamin A deficiency, hot climates, immobilisation, urinary tract anomalies)
Calcium from food does not increase your chance of having calcium oxalate stones. Normally, extra calcium that isn’t used by your bones and muscles goes to your kidneys and is flushed out with urine. When this doesn’t happen, the calcium stays in the kidneys and joins with other waste products to form a kidney stone.
- For calcium stones, risk factors vary by population. The main risk factor in the US is hypercalciuria (condition of elevated calcium in the urine), a hereditary condition present in 50% of men and 75% of women with calcium calculi; thus, patients with a family history of calculi are at increased risk of recurrent calculi 27). These patients have normal serum calcium, but urinary calcium is elevated > 250 mg/day (> 6.2 mmol/day) in men and > 200 mg/day (> 5.0 mmol/day) in women 28).
- Hypocitruria (urinary citrate < 350 mg/day [1820 μmol/day]), present in about 40 to 50% of calcium calculi-formers, promotes calcium calculi formation because citrate normally binds urinary calcium and inhibits the crystallization of calcium salts 29). The activity of citrate is thought to be related to its concentration in urine, where it exhibits a dual action, opposing crystal formation by both thermodynamic and kinetic mechanisms. Citrate retards stone formation by inhibiting the calcium oxalate nucleation process and the growth of both calcium oxalate and calcium phosphate stones, largely by its ability to bind with urinary calcium and reduce the free calcium concentration, thereby reducing the supersaturation of urine. Citrate binds to the calcium oxalate crystal surface, inhibiting crystal growth and aggregation 30). There is also evidence that citrate blocks the adhesion of calcium oxalate monohydrate crystals to renal epithelial cells 31). Medical interventions to increase urinary citrate are a primary focus in the medical management of urolithiasis 32). The amount of diet-derived citrate that may escape in body conversion to bicarbonate is reportedly minor 33). Nonetheless, a prior study reported increased urinary citrate after 1 week on 4 ounces lemon juice per day, diluted in 2 L water, in stone formers with hypocitraturia 34). Two retrospective studies showed an effect in calcium stone formers of lemon juice and/or lemonade consumption on urinary citrate 35), but a recent clinical trial showed no influence of lemonade on urinary citrate 36).
- Hypocitraturia, if severe and/or persistent, usually requires pharmacologic therapy in the form of potassium citrate, which enhances urine pH and also citrate excretion. The identification and promotion of consumption of fluids that add to the crystal inhibitory potential of urine is appealing, not only to promote fluid intake but to enhance urinary citrate excretion. Citric acid is a naturally-occurring organic acid present in multiple fruits, such as lemon, lime, grapefruit, tangerine, and orange and their juices 37). Data on the citric acid content of fresh fruit juices and commercially-available fruit juice beverages may therefore prove useful in constructing nutrition therapy regimens for calcium stone formers.
Lemon and lime juice, both from the fresh fruit and from juice concentrates, provide more citric acid per liter than ready-to-consume grapefruit juice, ready-to-consume orange juice, and orange juice squeezed from the fruit 38). Lemon and lime juices are rich sources of citric acid, containing 1.44 and 1.38 g/oz, respectively, comprising as much as 8% of the dry fruit weight 39). These data concur with those previously reported 40). As lemon and lime juice contain 38 and 35 mg potassium/oz, respectively, about the same as grapefruit juice and about 60% that of orange juice, ingestion of lemon or lime juice on a daily basis could provide dietary alkali that would decrease renal tubular reabsorption of citrate, resulting in enhanced urinary citrate excretion. The distribution of lemon or lime juice in ample water or other fluid, consumed throughout the day, would also add to the volume of fluids ingested, resulting in enhanced urine output 41) and reduced urine supersaturation.
Further research should determine the bioavailability of dietary citric acid from various sources and characterize the response to dietary citric acid in kidney stone formers who are hypocitraturic, as well as those who are normocitraturic. The impact of diet-derived citrate on urinary concentrations among calcium stone formers consuming different diets (e.g., high fruit/vegetable intake versus low fruit/vegetable intake; high meat intake versus low meat intake) should be assessed, as dietary patterns are known to influence urinary citrate concentrations 42).
- About 5 to 8% of calculi are caused by renal tubular acidosis. About 1 to 2% of patients with calcium calculi have primary hyperparathyroidism 43). Rare causes of hypercalciuria are sarcoidosis, vitamin D intoxication, hyperthyroidism, multiple myeloma, metastatic cancer, and hyperoxaluria.
- Hyperoxaluria (urinary oxalate > 40 mg/day [> 440 μmol/day]) can be primary or caused by excess ingestion of oxalate-containing foods (eg, rhubarb, spinach, cocoa, nuts and nut products, peanuts [peanuts are legumes not nuts], wheat bran, pepper, tea) or by excess oxalate absorption due to various enteric diseases (eg, bacterial overgrowth syndromes, chronic pancreatic or biliary disease) or ileojejunal (eg, bariatric) surgery.
- Other risk factors include taking high doses of vitamin C (ie, > 2000 mg/day), a calcium-restricted diet (possibly because dietary calcium binds dietary oxalate), and mild hyperuricosuria. Mild hyperuricosuria, defined as urinary uric acid > 800 mg/day (> 5 mmol/day) in men or > 750 mg/day (> 4 mmol/day) in women, is almost always caused by excess intake of purine (in proteins, usually from meat, fish, and poultry); it may cause calcium oxalate calculus formation (hyperuricosuric calcium oxalate nephrolithiasis) 44).
Uric acid stones
Uric acid is the end product of purine metabolism and is either derived from exogenous (dietary) sources or produced endogenously during cell turnover. For example, eating a lot of fish, shellfish, and meat—especially organ meat—may increase uric acid in urine. Chronic metabolic acidosis can result in protein metabolism and thus increased excretion of urate and formation of kidney stones 45). Pure uric acid stones are rare but recur frequently. Low urinary pH (pH < 5.5) – urine acidity – is the most common and important factor in uric acid kidney stone formation or rarely with severe hyperuricosuria (urinary uric acid > 1500 mg/day [> 9 mmol/day]), which crystallizes undissociated uric acid; in normouricosuric stone disease the primary defect seems to be in the renal excretion of ammonia and is linked to an insulin resistant state 46). Hyperuricosuria occurs in 10% of patients with calcium stones, where uric acid crystals form the nidus for deposition of calcium and oxalate. A history of gout doubles the risk of kidney stones in men 47). Uric acid crystals may comprise the entire calculus or, more commonly, provide a nidus on which calcium or mixed calcium and uric acid calculi can form.
Struvite stones or magnesium ammonium phosphate calculi (infection stones) may form after you have a urinary tract infection (UTI) caused by urea-splitting bacteria (eg, Proteus sp, Klebsiella sp) 48). They can develop suddenly and become large quickly. The struvite stones must be treated as infected foreign bodies and removed in their entirety. Unlike other types of calculi, magnesium ammonium phosphate calculi occur 3 times more frequently in women 49).
Cystine stones result from a disorder called cystinuria that is passed down through families. Cystinuria causes the amino acid cystine to leak through your kidneys and into the urine. Less than 3% of urinary tract stones are cystine stones 50).
Table 2. Composition of Kidney Stones
Percentage of All Calculi
Renal tubular acidosis
Renal tubular acidosis
Magnesium ammonium phosphate (struvite)
Urinary Tract Infection (UTI)
caused by urea-splitting bacteria
Urine pH < 5.5
Figure 3. Kidney with kidney stones
What Causes Kidney Stone
If you have a family history of kidney stones, you are more likely to develop them. You are also more likely to develop kidney stones again if you’ve had them once.
You may also be more likely to develop a kidney stone if you don’t drink enough liquids.
General risk factors for developing kidney stone include disorders that increase urinary salt concentration, either by increased excretion of calcium or uric acid salts, or by decreased excretion of urinary citrate.
You are more likely to develop kidney stones if you have these conditions, including:
- anatomical abnormalities that increase the risk of stone disease
- a blockage of the urinary tract
- chronic, or long-lasting, inflammation of the bowel
- cystic kidney diseases , which are disorders that cause fluid-filled sacs to form on the kidneys
- digestive problems or a history of gastrointestinal tract surgery
- gout, a disorder that causes painful swelling of the joints
- hypercalciuria , a condition that runs in families in which urine contains unusually large amounts of calcium; this is the most common condition found in
- people who form calcium stones
- hyperoxaluria , a condition in which urine contains unusually large amounts of oxalate
- hyperparathyroidism, a condition in which the parathyroid glands release too much parathyroid hormone, causing extra calcium in the blood
- hyperuricosuria, a disorder in which too much uric acid is in the urine
- repeated, or recurrent, urinary tract infections (UTIs)
- renal tubular acidosis, a disease that occurs when the kidneys fail to remove acids into the urine, which causes a person’s blood to remain too acidic.
Anatomical abnormalities that increase the risk of kidney stone disease
- Obstruction of the pelviureteral junction
- Hydronephrotic renal pelvis or calices
- Calyceal diverticulum
- Horseshoe kidney
- Vesicoureteral reflux
- Ureteral stricture
- Tubular ectasia (medullary sponge kidney)
Medications Associated with Kidney Stone Formation
Table 3. Medications Associated with Kidney Stone Formation
|Type of medication||Examples|
Agents that decrease uric acid production
Laxatives (specific to ammonium urate stones), especially if abused
Overuse of any laxative resulting in electrolyte losses
Sulfonamides, ampicillin, amoxicillin, ceftriaxone (Rocephin), quinolones, furans, pyridines
Carbonic anhydrase inhibitors
Acetazolamide, topiramate (Topamax)
Ephedra alkaloids (banned in the United States)
Herbal products used as stimulants and appetite suppressants
Potassium channel blockers
Amiodarone, sotalol (Betapace), dalfampridine (Ampyra; multiple sclerosis therapy)
Reverse transcriptase inhibitors and protease inhibitors
HAART (highly active antiretroviral therapy)
Various therapies for type 2 diabetes mellitus
Does Obesity Increase Risk and Will Weight Loss Reduce Your Risk for Kidney Stones ?
Obesity contributes to risk of kidney stones more than dietary factors. The associated changes in body composition pose biophysical challenges associated with disturbed thermogenesis and dehydration. Because body fat is hydrophobic, the proportion of body water decreases with increasing obesity, which can lead to dehydration 53). Additionally, the decrease in surface area to body volume complicates heat exchange and metabolic rate 54). Obesity is a proinflammatory state associated with electrolyte imbalances and altered urine chemistry. Obese persons with kidney stones are predisposed to hyperuricemia, gout, hypocitraturia, hyperuricosuria, and uric acid stones 55). A recent retrospective analysis found that patients with diabetes and kidney stones excrete more oxalate and have lower urine pH, which is partly a result of higher sulfate excretion and less acid excreted as ammonium ions 56), 57).Patients with kidney disease who are obese or have diabetes may have a lesser genetic predisposition to kidney stones and greater responsiveness to environmental modification, such as a healthy diet and hydration.
Weight loss may improve or undermine management of kidney stones, depending on how it is achieved. Weight loss could be detrimental to prevention of kidney stones if associated with a high animal protein diet, laxative abuse, rapid loss of lean tissue, or poor hydration. High acid diets, such as the Atkins diet, increase the risk of uric acid stones 58). Therefore, diet advice should be based on the type of kidney stone.
Should people with a history of kidney stones reduce their fructose intake ?
Increased dietary fructose has been associated with up to a 38 percent higher risk of kidney stones 59). Increased fructose intake increases urinary calcium excretion in persons with magnesium deficiency, and fructose is the only dietary carbohydrate known to raise uric acid levels. Additionally, sugar-sweetened beverages and orange juice have been linked to gout 60).
Hypercalciuria is defined as excretion of urinary calcium exceeding 200 mg in a 24 hour collection or an excess of 4 mg calcium/kg/24 hour 61).
Hypercalciuria is the most common metabolic abnormality in patients with calcareous stones and results from various mechanisms 62).
Absorptive hypercalciuria—Increased absorption of calcium from the gut results in increased circulating calcium, resulting in increased renal filtered load. The exact mechanism is unknown but seems to be inherited in an autosomal dominant fashion, and the jejunal mucosa is hyper-responsive to vitamin D. Absorptive hypercalciuria is very common, but most patients remain asymptomatic and do not experience stone formation.
Renal hypercalciuria—Increased excretion of calcium in urine results from impaired renal tubular absorption of calcium. This occurs in about 2% of patients with recurrent stone formation.
Resorptive hypercalciuria—Increased resorption of bone occurs as a result of primary hyperparathyroidism. This occurs in about 5% of patients with recurrent stone formation. The risk of renal stones is increased in primary hyperparathyroidism and returns to baseline about 10 years after parathyroidectomy. Patients who had stones before undergoing parathyroidectomy have a 27 times greater risk of stone formation after parathyroidectomy than do patients without hyperparathyroidism 63).
Uric acid is the end product of purine metabolism and is either derived from exogenous (dietary) sources or produced endogenously during cell turnover. Chronic metabolic acidosis can result in protein metabolism and thus increased excretion of urate and formation of kidney stones.10 Pure uric acid stones are rare but recur frequently. Low urinary pH (pH < 5.5) is the most common and important factor in uric acid nephrolithiasis; in normouricosuric stone disease the primary defect seems to be in the renal excretion of ammonia and is linked to an insulin resistant state. Hyperuricosuria occurs in 10% of patients with calcium stones, where uric acid crystals form the nidus for deposition of calcium and oxalate. A history of gout doubles the risk of kidney stones in men.
Hyperoxaluria is defined as urinary excretion of oxalate in excess of 45 mg/day 64). On the basis of the mechanism, it is classified as follows.
Enteric hyperoxaluria—This results from increased intestinal absorption due to ileal disease (Crohn’s disease, ileal bypass) or short bowel syndrome, low calcium intake, or gastrointestinal decolonisation of Oxalobacter formigenes. Oxalobacter is an intestinal bacterium that degrades dietary oxalate, and decolonisation of the gut results in increased absorption of oxalate. Oral administration of Oxalobacter has been shown to decrease urinary oxalate concentration in animals and humans 65), 66).
Increased ingestion (oxalate gluttons)—Dietary oxalate contributes to about half of the urinary oxalate and is inversely proportional to calcium intake in healthy people without gastrointestinal disease 67). Spinach, rhubarb, beets, chocolate, nuts, tea, wheat bran, strawberries, and soya foods are known to increase urinary oxalate concentrations 68). Vitamin C supplementation may increase urinary oxalate excretion and the risk of calcium oxalate crystallisation in patients who form calcium stones 69). Ingestion of grapefruit juice increases excretion of both oxalate and citrate in urine with no net change in its lithogenicity 70).
Primary hyperoxaluria—This is an inborn error of metabolism (glycolic aciduria).
In experimental animals, testosterone promotes stone formation by suppressing osteopontin expression in the kidney and increasing urinary oxalate excretion. Oestrogen seems to inhibit stone formation by increasing osteopontin expression in the kidney and decreasing urinary oxalate excretion 71).
Hypocitriuria is defined as urinary citrate excretion of < 250 mg in 24 hours. Urinary citrate forms a soluble complex with calcium that inhibits the formation and propagation of crystals 72). It is a common correctable cause of recurrent pure calcium phosphate or brushite stones. Women excrete more citrate and have lower incidence of stone formation than men. Urinary citrate is mainly derived endogenously through the tricarboxylic acid cycle and is excreted by renal tubular cells. Intracellular acidosis, acidic diets (diets rich in animal proteins), and hypokalaemia decrease urinary citrate excretion. Fruits such as oranges and grapefruits are the main exogenous sources of urinary citrate. Hormonal replacement therapy in postmenopausal women results in higher urinary calcium excretion, but it also increases urinary excretion of citrate and leads to net inhibition of crystal precipitation, thereby decreasing the risk of calcium stones 73).
Struvite (triple phosphate) and cystine stones
Various anatomical abnormalities promote urine stasis and increase the risk of stone formation by promoting precipitation of crystals. Urinary infection with urea splitting organisms (Proteus, Klebsiella, Serratia, and Mycoplasma) creates alkaline urine that promotes the formation of struvite stones. Urinary saturation with struvite occurs only when supranormal excretion of ammonia and alkaline urine occur together. Alkalaemia suppresses renal ammoniagenesis, but the hydrolysis of urea by bacteria liberates ammonia that alkalises urine.
Cystinuria (cystine stones) is an autosomal recessive trait, with an inborn error in the transport of dicarboxylic acids—cystine, ornithine, lysine, and arginine, commonly known as “COLA.” The low solubility of cystine results in its precipitation and stone formation.
Various urinary glycoproteins (Tamm-Horsfall proteins, bikunin, nephrocalcin, urinary prothrombin fragment I) are inhibitors of stone formation. Their deficiency may promote stone formation.
Drugs that may increase the risk of stone disease
- Decongestants: ephedrine, guaifenesin
- Diuretics: triamterene
- Protease inhibitors: indinavir
- Anticonvulsants: felbamate, topiramate, and zonisamide
What are the disordered physiological processes associated with Kidney Stone
Kidney stones may remain within the kidney or renal collecting system or be passed into the ureter and bladder. During passage, the stones may irritate the ureter and may become lodged, obstructing urine flow and causing hydroureter and sometimes hydronephrosis. Common areas of lodgment include the following:
- Ureteropelvic junction
- Distal ureter (at the level of the iliac vessels)
- Ureterovesical junction
Larger kidney stones are more likely to become lodged. Typically, a kidney stone must have a diameter > 5 mm to become lodged.
Kidney stones ≤ 5 mm are likely to pass spontaneously.
Even partial obstruction causes decreased glomerular filtration, which may persist briefly after the calculus has passed. With hydronephrosis and elevated glomerular pressure, renal blood flow declines, further worsening renal function. Generally, however, in the absence of infection, permanent renal dysfunction occurs only after about 28 days of complete obstruction.
Secondary infection can occur with long-standing obstruction, but most patients with calcium-containing calculi do not have infected urine.
What are the complications of kidney stones ?
Complications of kidney stones are rare if you seek treatment from a health care professional before problems occur.
If kidney stones are not treated, they can cause:
- hematuria, or blood in the urine
- severe pain
- urinary tract infections (UTIs), including kidney infections (pyelonephritis)
- loss of kidney function
What are Symptoms and Signs of Kidney Stone
Large kidney stones remaining in the kidney or renal collecting system are often asymptomatic unless they cause obstruction and/or infection 74). Severe pain, often accompanied by nausea and vomiting, usually occurs when kidney stones pass into the ureter and cause acute obstruction. Sometimes gross hematuria also occurs.
Pain (renal colic) is of variable intensity but is typically excruciating and intermittent, often occurs cyclically, and lasts 20 to 60 min. Nausea and vomiting are common. Pain in the flank or kidney area that radiates across the abdomen suggests upper ureteral or renal pelvic obstruction. Pain that radiates along the course of the ureter into the genital region suggests lower ureteral obstruction. Suprapubic pain along with urinary urgency and frequency suggests a distal ureteral, ureterovesical, or bladder stone.
The person with kidney stone may be in obvious extreme discomfort, often ashen and diaphoretic (sweating heavily). The person with kidney stone with renal colic may be unable to lie still and may pace, writhe, or constantly shift position. The abdomen may be somewhat tender on the affected side as palpation increases pressure in the already-distended kidney (costovertebral angle tenderness), but peritoneal signs (guarding, rebound, rigidity) are lacking.
For some patients, the first symptom is hematuria or either gravel or a calculus in the urine. Other patients may have symptoms of a urinary tract infection, such as fever, dysuria (painful urination) or cloudy or foul-smelling urine.
Symptoms of kidney stones include:
- sharp pains in your back, side, lower abdomen, or groin
- pink, red, or brown blood in your urine, also called hematuria
- a constant need to urinate
- pain while urinating
- inability to urinate or can only urinate a small amount
- cloudy or bad-smelling urine.
See a health care professional right away if you have any of these symptoms. These symptoms may mean you have a kidney stone or a more serious condition.
Your pain may last for a short or long time or may come and go in waves. Along with pain, you may have
Other symptoms include:
How Kidney Stone is Diagnosed
Health care professionals may use lab or imaging tests to diagnose kidney stones.
Urine tests can show whether your urine contains high levels of minerals that form kidney stones. Urine and blood tests can also help a health care professional find out what type of kidney stones you have.
Urinalysis. Urinalysis involves a health care professional testing your urine sample. You will collect a urine sample at a doctor’s office or at a lab, and a health care professional will test the sample. Urinalysis can show whether your urine has blood in it and minerals that can form kidney stones. White blood cells and bacteria in the urine mean you may have a urinary tract infection. Macroscopic or microscopic hematuria is common, but urine may be normal despite multiple kidney stones. Pyuria (pus in urine) with or without bacteria may be present. Pyuria suggests infection, particularly if combined with suggestive clinical findings, such as foul-smelling urine or a fever. A stone and various crystalline substances may be present in the sediment. If so, further testing is usually necessary because the composition of the calculus and crystals cannot be determined conclusively by microscopy. The only exception is when typical hexagonal crystals of cystine are found in a concentrated, acidified specimen, confirming cystinuria.
Blood tests. A health care professional may take a blood sample from you and send the sample to a lab to test. The blood test can show if you have high levels of certain minerals in your blood that can lead to kidney stones.
Health care professionals use imaging tests to find kidney stones. The tests may also show problems that caused a kidney stone to form, such as a blockage in the urinary tract or a birth defect. You do not need anesthesia for these imaging tests.
Computed tomography (CT) scans. Noncontrast helical CT scan is the initial imaging study. This study can detect the location of a calculus as well as the degree of obstruction. Moreover, helical CT scan may also reveal another cause of the pain (eg, aortic aneurysm). For patients who have recurrent calculi, cumulative radiation exposure from multiple CT scans is a concern. However, the routine use of low-dose renal CT can meaningfully reduce cumulative radiation dose with little loss of sensitivity 75). For patients with typical symptoms, ultrasonography or plain abdominal x-rays can usually confirm presence of a calculus with minimal or no radiation exposure. MRI may not identify calculi. Although a CT scan without contrast medium is most commonly used to view your urinary tract, a health care professional may give you an injection of contrast medium. Contrast medium is a dye or other substance that makes structures inside your body easier to see during imaging tests. You’ll lie on a table that slides into a tunnel-shaped device that takes the x-rays. CT scans can show the size and location of a kidney stone, if the stone is blocking the urinary tract, and conditions that may have caused the kidney stone to form.
Abdominal x-ray. An abdominal x-ray is a picture of the abdomen that uses low levels of radiation and is recorded on film or on a computer. An x-ray technician takes an abdominal x-ray at a hospital or outpatient center, and a radiologist reads the images. Although most urinary calculi are demonstrable on plain x-ray, neither their presence nor their absence obviates the need for more definitive imaging, so this study can be avoided except in some patients with suspected recurrent calculi. Both renal ultrasonography and excretory urography (previously called intravenous urography) can identify calculi and hydronephrosis. However, ultrasonography is less sensitive for small or ureteral calculi in patients without hydronephrosis, and excretory urography is time consuming and exposes the patient to the risk of IV contrast agents. Abdominal x-rays can show the location of kidney stones in the urinary tract. Not all stones are visible on abdominal x-ray. These studies are generally used when helical CT is unavailable.
How To Treat Kidney Stone
The American Urological Association produces a clincal guideline to provide doctors with a clinical framework for the diagnosis, prevention and follow-up of adult patients with kidney stones based on the best available published literature 76)).
Identifying the cause
The kidney stone is obtained by straining the urine (or, if necessary, during operative removal) and sent to the laboratory for stone analysis. Some calculi are brought in by patients. Urine specimens that show microscopic crystals are sent for crystallography.
In patients with a single calcium kidney stone and no additional risk factors for kidney stones, evaluation to exclude hyperparathyroidism is sufficient. Evaluation entails urinalysis and determination of plasma calcium concentration on 2 separate occasions. Predisposing factors, such as recurrent calculi, a diet high in animal protein, or use of vitamin C or D supplements, should be sought.
Patients with a strong family history of calculi, conditions that might predispose to calculi formation (eg, sarcoidosis, bone metastases, multiple myeloma), or conditions that would make it difficult to treat calculi (eg, solitary kidney, urinary tract anomalies) require evaluation for all possible causative disorders and risk factors. This evaluation should include serum electrolytes, uric acid, and calcium on 2 separate occasions. Follow-up determination of parathyroid hormone levels is done if necessary. Urine tests should include routine urinalysis and 2 separate 24-h urine collections to determine urine volume, pH, and excretion of calcium, uric acid, citrate, oxalate, sodium, and creatinine 77).
Acute Management of Kidney Stones in Adults
Oral hydration and pain management are part of the acute treatment of all stone types (Table 3). For stones measuring 10 mm or less, antispasmodics such as calcium channel blockers and alpha blockers relax the smooth muscle of the ureters and have been shown to hasten stone passage by five to seven days 78). Co-administration of oral corticosteroids leads to little or no improvement in outcomes 79). People who are unable to take oral fluids or medications and people with low blood pressure or other signs of early hemodynamic instability should be treated intravenously. If signs of possible infection are present (e.g., fever, pyuria), initial management should include empiric antibiotics that cover gram-negative bacilli (e.g., Enterobacteriaceae species) and gram-positive cocci (e.g., staphylococci, enterococci) according to local susceptibility patterns. Referral to a urologist should be expedited if the patient also shows radiologic evidence of obstruction (hydronephrosis).
Table 4. Acute Management of Kidney Stones in Adults
Oral intake of water, or intravenous normal saline if patient is unable to take oral fluids
At least 2 L of water per 24 hours
0.9% normal saline solution if blood pressure is low; consider decreasing sodium chloride in patients with calciuria (5% dextrose in water and 0.45% normal saline)
Antispasmodics to facilitate stone passage*
4 mg orally per day
0.4 mg orally per day
Calcium channel blockers
Nifedipine (Procardia, sustained release)
30 mg orally per day
One or two tablets (5 to 10 mg codeine/325 to 500 mg acetaminophen) orally every four to six hours as needed
5 to 10 mg orally every four to six hours as needed
Note: People who are unable to take oral medications and people with low blood pressure or other signs of early hemodynamic instability should be treated intravenously.
*—Often administered for up to four weeks before performing follow-up imaging studies to determine whether the stone has passed.
†—Avoid using nonsteroidal anti-inflammatory drugs because they tend to lower kidney blood flow and glomerular filtration.
Further evaluation identifies modifiable risk factors and guides individualized treatment and prevention. The medical history should identify conditions associated with increased risk of kidney stones (e.g., inflammatory bowel disease, bowel surgery, gout, diabetes mellitus, obesity or recent changes in weight, metabolic syndromes, hyperparathyroidism-associated conditions, frequent urinary tract infections, chronic kidney disease) 81). A family medical history should also be obtained.
A medication history establishes temporal associations; identifies medications recently discontinued, off-label use of medications, and use of herbal preparations and supplements; and screens for illicit drug use. Medications contribute to kidney stones (Table 4) through various mechanisms by forming urine crystals and altering urine characteristics (e.g., changing urine pH, reducing urine volume) 82), 83). For example, carbonic anhydrase inhibitors contribute to calcium phosphate stone formation by causing a mild systemic acidosis and paradoxically high urine pH, hypercalciuria, and low urine citrate 84), 85). Some antibiotics may increase urine oxalate by reducing the intestinal bacteria that break down oxalate.
1. A clinician should perform a screening evaluation consisting of a detailed medical and dietary history, serum chemistries and urinalysis on a patient newly diagnosed with kidney or ureteral stones.
2. Clinicians should obtain serum intact parathyroid hormone (PTH) level as part of the screening evaluation if primary hyperparathyroidism is suspected.
3. When a stone is available, clinicians should obtain a stone analysis at least once.
4. Clinicians should obtain or review available imaging studies to quantify stone burden.
5. Clinicians should perform additional metabolic testing in high-risk or interested first-time stone formers and recurrent stone formers.
6. Metabolic testing should consist of one or two 24-hour urine collections obtained on a random diet and analyzed at minimum for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium and creatinine.
7. Clinicians should not routinely perform “fast and calcium load” testing to distinguish among types of hypercalciuria.
8. Clinicians should recommend to all stone formers a fluid intake that will achieve a urine volume of at least 2.5 liters daily.
9. Clinicians should counsel patients with calcium stones and relatively high urinary calcium to limit sodium intake and consume 1,000-1,200 mg per day of dietary calcium.
10. Clinicians should counsel patients with calcium oxalate stones and relatively high urinary oxalate to limit intake of oxalate-rich foods and maintain normal calcium consumption.
11. Clinicians should encourage patients with calcium stones and relatively low urinary citrate to increase their intake of fruits and vegetables and limit non-dairy animal protein.
12. Clinicians should counsel patients with uric acid stones or calcium stones and relatively high urinary uric acid to limit intake of non-dairy animal protein.
13. Clinicians should counsel patients with cystine stones to limit sodium and protein intake.
14. Clinicians should offer thiazide diuretics to patients with high or relatively high urine calcium and recurrent calcium stones.
15. Clinicians should offer potassium citrate therapy to patients with recurrent calcium stones and low or relatively low urinary citrate.
16. Clinicians should offer allopurinol to patients with recurrent calcium oxalate stones who have hyperuricosuria and normal urinary calcium.
17. Clinicians should offer thiazide diuretics and/or potassium citrate to patients with recurrent calcium stones in whom other metabolic abnormalities are absent or have been appropriately addressed and stone formation persists.
18. Clinicians should offer potassium citrate to patients with uric acid and cystine stones to raise urinary pH to an optimal level.
19. Clinicians should not routinely offer allopurinol as first-line therapy to patients with uric acid stones.
20. Clinicians should offer cystine-binding thiol drugs, such as alpha-mercaptopropionylglycine (tiopronin), to patients with cystine stones who are unresponsive to dietary modifications and urinary alkalinization, or have large recurrent stone burdens.
21. Clinicians may offer acetohydroxamic acid to patients with residual or recurrent struvite stones only after surgical options have been exhausted.
22. Clinicians should obtain a single 24-hour urine specimen for stone risk factors within six months of the initiation of treatment to assess response to dietary and/or medical therapy.
23. After the initial follow-up, clinicians should obtain a single 24-hour urine specimen annually or with greater frequency, depending on stone activity, to assess patient adherence and metabolic response.
24. Clinicians should obtain periodic blood testing to assess for adverse effects in patients on pharmacological therapy.
25. Clinicians should obtain a repeat stone analysis, when available, especially in patients not responding to treatment.
26. Clinicians should monitor patients with struvite stones for reinfection with urease-producing organisms and utilize strategies to prevent such occurrences.
27. Clinicians should periodically obtain follow-up imaging studies to assess for stone growth or new stone formation based on stone activity (plain abdominal imaging, renal ultrasonography or low dose computed tomography [CT scan]).
Medical expulsive therapy
Although increasing fluids (either oral or IV) has traditionally been recommended, increased fluid administration has not been proven to speed the passage of calculi. Patients with calculi < 1 cm in diameter who have no infection or obstruction, whose pain is controlled with analgesics, and who can tolerate liquids can be treated at home with analgesics and alpha-receptor blockers (eg, tamsulosin 0.4 mg po once/day) to facilitate calculus passage. Calculi that have not passed within 6 to 8 wk typically require removal. In patients with infection and obstruction, initial treatment is relief of obstruction with a ureteral stent and treatment of the infection followed by removal of calculi as soon as possible.
Kidney stone removal
The technique used for removal depends on the location and size of the kidney stone. About 10-20% of all kidney stones need radiological or surgical intervention to remove the stone. Techniques include shock wave lithotripsy and, to ensure complete removal or for larger calculi, endoscopic techniques. Endoscopic techniques may involve rigid or flexible ureteroscopes (endoscopes) and may involve direct-vision removal (basketing), fragmentation with some sort of lithotripsy device (eg, pneumatic, ultrasonic, laser), or both.
For symptomatic calculi < 1 cm in diameter in the renal collecting system or proximal ureter, shock wave lithotripsy is a reasonable first option for therapy.
For larger calculi or if shock wave lithotripsy is unsuccessful, ureteroscopy (done in a retrograde fashion) with holmium laser lithotripsy is usually used. Sometimes removal is possible using an endoscope inserted anterograde through the kidney.
For renal stones > 2 cm, percutaneous nephrolithotomy, with insertion of a nephroscope directly into the kidney, is the treatment of choice.
For midureteral calculi, ureteroscopy with holmium laser lithotripsy is usually the treatment of choice. Shock wave lithotripsy is an alternative.
For distal ureteral calculi, endoscopic techniques (ureteroscopy), such as direct removal and use of intracorporeal lithotripsy (eg, pneumatic, electrohydraulic, laser), are considered by many to be the procedures of choice. Shock wave lithotripsy can also be used.
Kidney stone dissolution
Uric acid stones in the upper or lower urinary tract occasionally may be dissolved by prolonged alkalinization of the urine with potassium citrate 20 mEq po bid to tid, but chemical dissolution of calcium calculi is not possible and of cystine calculi is difficult.
How To Prevent Getting a Kidney Stone
In a patient who has passed a first calcium calculus, the likelihood of forming a 2nd calculus is about 15% at 1 yr, 40% at 5 yr, and 80% at 10 yr. Drinking large amounts of fluids— that will achieve a urine volume of at least 2.5 liters daily—is recommended for prevention of all stones 86). Recovery and analysis of the calculus, measurement of calculus-forming substances in the urine, and the clinical history are needed to plan other prophylactic measures.
In < 3% of patients, no metabolic abnormality is found. These patients seemingly cannot tolerate normal amounts of calculus-forming salts in their urine without crystallization. Thiazide diuretics, potassium citrate, and increased fluid intake may reduce their calculus production rate.
For hypercalciuria, patients may receive thiazide diuretics (eg, chlorthalidone 25 mg po once/day or indapamide 1.25 mg po once/day) to lower urine calcium excretion and thus prevent urinary supersaturation with calcium oxalate. Patients are encouraged to increase their fluid intake to ≥ 3 L/day. A diet that is low in sodium and high in potassium is recommended. Even with a high potassium intake, supplementation with potassium citrate is recommended to prevent hypokalemia. Restriction of dietary animal protein is also recommended.
For patients with hypocitruria, potassium citrate (20 mEq po bid) enhances citrate excretion. A normal calcium intake (eg, 1000 mg or about 2 to 3 dairy servings per day) is recommended, and calcium restriction is avoided. Oral orthophosphate has not been thoroughly studied.
Hyperoxaluria prevention varies. Patients with small-bowel disease can be treated with a combination of high fluid intake, calcium loading (usually in the form of calcium citrate 400 mg po bid with meals), cholestyramine, and a low-oxalate, low-fat diet. Hyperoxaluria may respond to pyridoxine 100 to 200 mg po once/day, possibly by increasing transaminase activity, because this activity is responsible for the conversion of glyoxylate, the immediate oxalate precursor, to glycine.
In hyperuricosuria, intake of animal protein should be reduced. If the diet cannot be changed, allopurinol 300 mg each morning lowers uric acid production. For uric acid calculi, the urine pH must be increased to between 6 and 6.5 by giving an oral alkalinizing drug that contains potassium (eg, potassium citrate 20 mEq bid) along with increased fluid intake.
Infection with urea-splitting bacteria requires culture-specific antibiotics and complete removal of all calculi. If eradication of infection is impossible, long-term suppressive therapy (eg, with nitrofurantoin) may be necessary. In addition, acetohydroxamic acid can be used to reduce the recurrence of struvite calculi.
To prevent recurrent cystine calculi, urinary cystine levels must be reduced to < 250 mg cystine/L of urine. Any combination of increasing urine volume along with reducing cystine excretion (eg, with alpha-mercaptopropionylglycine or penicillamine) should reduce the urinary cystine concentration.
For prevention of calcium oxalate, cystine, and uric acid stones, urine should be alkalinized
For prevention of calcium oxalate, cystine, and uric acid stones, urine should be alkalinized [increase urine pH to 6.5 to 7] 87), 88). Western diets are characteristically high in acid-producing foods, such as grains, dairy products, legumes, and meat. Alkalinizing urine involves eating a diet high in fruits and vegetables, taking supplemental or prescription citrate, or drinking alkaline mineral waters 89).
How To Alkalinize Your Urine
Alkalinize urine (i.e., increase urine pH to 6.5 to 7) with dietary changes or oral supplementation, or until 24-hour urine citrate levels are in the normal range:
- Potassium citrate: 10 to 20 mEq orally with meals (prescription required)
- Calcium citrate: two 500-mg tablets per day with meals (each tablet contains 120 mg of calcium and 6 mEq of bicarbonate)
For prevention of calcium phosphate and struvite stones, urine should be acidified
For prevention of calcium phosphate and struvite stones, urine should be acidified [lower urine pH to 7 or less] 90). Cranberry juice or betaine can lower urine pH without the adverse effects associated with acid-producing foods. Although table salt (sodium chloride) also lowers urine pH, it can increase blood pressure, insulin excretion, and urine calcium excretion.
How to Acidify Your Urine
Acidify urine (i.e., lower urine pH to 7 or less) with dietary changes or oral supplementation:
- Cranberry juice: at least 16 oz per day
- Betaine: 650 mg orally three times per day with meals
Can Bacterial Infection Trigger Recurrence ?
Bacteria exert both pathogenic and protective roles. Struvite stones are associated with recurrent infections because of high urinary pH levels from urease splitting bacteria and the body’s inability to rid the urinary tract of bacteria that become embedded in the stones 91).
Oxalobacter formigenes is an anaerobic bacterium that colonizes the intestinal tract, where it metabolizes oxalate to formate and carbon dioxide. Absence of O. formigenes colonization predisposes persons to oxalate stones 92). Preliminary studies of O. formigenes ingestion in healthy patients 93) and in patients with primary hyperoxaluria demonstrated up to a 90 percent decrease in urinary oxalate levels 94). Larger studies of this potential therapy are ongoing.
Specific treatments to prevent recurrent stones
- Oral administration of potassium citrate—increases urine pH and citrate excretion in the urine.
- Thiazide diuretics—decrease urinary calcium excretion by augmenting tubular reabsorption of calcium, but do not decrease intestinal absorption in absorptive hypercalciuria; the effect may be attenuated or lost after two or more years of treatment
- Addition of potassium citrate may help to control the diuretic induced hypokalaemia
- If magnesium loss is a concern because of chronic diuretic use, consider potassium magnesium citrate
- Potassium phosphate—may suppress calcitriol synthesis and thereby decrease calcium absorption
Hyperuricaemia or hyperuricosuria
- Allopurinol—to inhibit uric acid synthesis and decrease urinary uric acid excretion
- Potassium citrate should be given in addition to increase urine pH, as uric acid precipitates in acidic urine
- No specific drugs are available to reduce oxalate excretion in the urine
- Pyridoxine, a cofactor in the alanine-glycoxylate pathway, may reduce production of oxalate by inducing enzyme activity; in an observational study, high intake of vitamin B6 (> 40 mg/day) was inversely associated with risk of oxalate stone formation in women
- Calcium supplementation (250-1000 mg four times a day) to control enteric hyperoxaluria; urinary oxalate may decrease, but a concurrent rise in calcium may negate the beneficial effect
- Cholestyramine reduces intestinal absorption of oxalate, but no trials have shown its efficacy in preventing recurrent stones
- Probiotic treatment with Oxalobacter formigenes has recently been shown to significantly reduce oxalate excretion in both animals and humans; however, trials are pending to show its role in clinical practice 95), 96).
- Potassium citrate—to increase citrate excretion
- Treatment of infection is mandatory and may be needed in the long term
- Acetohydroxamic acid, a urease inhibitor, has been shown to reduce the urinary saturation of struvite but is associated with high frequency of side effects (deep vein thrombosis, haemolytic anaemia), which limits its use.
- Treatment must include increasing urine output to about 3 l/day and adequate alkalinisation (urine pH > 7.0) with potassium citrate.
- In addition, specific agents such as α mercaptopropionylglycine or d-penicillamine that form soluble complexes with cystine are used.
What is Renal Tubular Acidosis
Renal tubular acidosis is a disease that occurs when the kidneys fail to excrete acids into the urine or reabsorption of filtered bicarbonate is impaired, which causes a person’s blood to remain too acidic resulting in leading to a chronic metabolic acidosis 97). Without proper treatment, chronic acidity of the blood leads to growth retardation, kidney stones, bone disease, chronic kidney disease, and possibly total kidney failure. About 5 to 8% of kidney stones are caused by renal tubular acidosis 98).
The body’s cells use chemical reactions to carry out tasks such as turning food into energy and repairing tissue. These chemical reactions generate acids. Some acid in the blood is normal, but too much acid—acidosis—can disturb many bodily functions. Healthy kidneys help maintain acid-base balance by excreting acids into the urine and returning bicarbonate—an alkaline, or base, substance—to the blood. This “reclaimed” bicarbonate neutralizes much of the acid that is created when food is broken down in the body. The movement of substances like bicarbonate between the blood and structures in the kidneys is called transport.
The good news is that medical treatment can indeed reverse the effects of renal tubular acidosis.
How is Renal tubular acidosis diagnosed ?
To diagnose renal tubular acidosis, doctors check the acid-base balance in blood and urine samples. If the blood is more acidic than it should be and the urine less acidic than it should be, renal tubular acidosis may be the reason, but additional information is needed to rule out other causes. If renal tubular acidosis is the reason, additional information about the sodium, potassium, and chloride levels in the urine and the potassium level in the blood will help identify which type of renal tubular acidosis a person has. In all cases, the first goal of treatment is to neutralize acid in the blood, but different treatments may be needed to address the different underlying causes of acidosis.
What are the types of renal tubular acidosis ?
Type 1: Classical Distal Renal Tubular Acidosis (Rare)
Type 1 is also called classical distal renal tubular acidosis. “Distal,” which means distant, refers to the point in the urine-forming tube of the kidney where the defect occurs—relatively distant from the point where fluid from the blood enters the tiny tube, or tubule, that collects fluid and wastes to form urine.
This disorder may be inherited as a primary disorder or may be one symptom of a disease that affects many parts of the body. Researchers have discovered abnormal genes responsible for the inherited forms of the disease. More often, however, classical distal renal tubular acidosis occurs as a result of systemic diseases—diseases that affect many organ systems—like the autoimmune disorders Sjögren’s syndrome and lupus, which also attack the distal tubule.
Other diseases and conditions associated with classical distal renal tubular acidosis include sickle cell anemia, hyperparathyroidism, hyperthyroidism, chronic active hepatitis, primary biliary cirrhosis, a hereditary form of deafness, analgesic nephropathy, rejection of a transplanted kidney, renal medullary cystic disease, obstructive uropathy, and chronic urinary tract infections. Many of these conditions cause abnormal calcium deposits to build up in the kidney and impair distal tubule function.
A major consequence of classical distal renal tubular acidosis is a low blood potassium level. The level drops if the kidneys excrete too much potassium into urine instead of returning it to the blood supply. Because potassium helps regulate nerve and muscle health and heart rate, low levels can cause extreme weakness, irregular heartbeat, paralysis, and even death.
Untreated classical distal renal tubular acidosis causes growth retardation in children and progressive kidney and bone disease in adults. Restoring normal growth and preventing kidney stones are the major goals of therapy. If acidosis is corrected with sodium bicarbonate or sodium citrate, then low blood potassium, salt depletion, and calcium leakage into urine will be corrected. This alkali therapy also helps decrease the development of kidney stones and stabilizes kidney function so kidney failure does not progress. Infants may need potassium supplements, but older children and adults rarely do because alkali therapy prevents the kidney from excreting potassium into the urine.
Type 2: Proximal Renal Tubular Acidosis (Very Rare)
Type 2 is also called proximal renal tubular acidosis. The word “proximal,” which means near, indicates that the defect is closer to the point where fluid and wastes from the blood enter the tubule.
This form of renal tubular acidosis occurs most frequently in children as part of a disorder called Fanconi’s syndrome. The features of Fanconi’s syndrome include the abnormal excretion of glucose, amino acids, citrate, and phosphate into the urine, as well as vitamin D deficiency and low blood-potassium.
Proximal renal tubular acidosis can also result from inherited disorders that disrupt the body’s normal breakdown and use of nutrients. Examples include the rare disease cystinosis, in which cystine crystals are deposited in bones and other tissues; hereditary fructose intolerance; and Wilson disease.
Proximal renal tubular acidosis also occurs in patients treated with ifosfamide, a drug used in chemotherapy. A few older drugs—such as acetazolamide or outdated tetracycline—can also cause proximal renal tubular acidosis. In adults, proximal renal tubular acidosis may complicate diseases like multiple myeloma, or it may occur in people who experience chronic rejection of a transplanted kidney.
When possible, identifying and correcting the underlying causes are important steps in treating the acquired forms of proximal renal tubular acidosis. The diagnosis is based on the chemical analysis of blood and urine samples. Children with this disorder would likely receive large doses of an oral alkali, such as sodium bicarbonate or potassium citrate, to treat acidosis and prevent bone disorders, kidney stones, and growth failure. Correcting acidosis and low potassium levels restores normal growth patterns, allowing bone to mature while preventing further renal disease. Vitamin D supplements may also be needed to help prevent bone problems.
Type 3 Renal Tubular Acidosis
Type 3 is rarely used as a classification because it is now thought to be a combination of type 1 and type 2.
Type 4: Hyperkalemic Renal Tubular Acidosis (Common)
Type 4 is also called hyperkalemic renal tubular acidosis and is caused by a generalized transport abnormality of the distal tubule. The transport of electrolytes such as sodium, chloride, and potassium that normally occurs in the distal tubule is impaired. This form is distinguished from classical distal renal tubular acidosis and proximal renal tubular acidosis because it results in high levels of potassium in the blood instead of low levels. Either low potassium—hypokalemia—or high potassium—hyperkalemia—can be a problem because potassium is important in regulating heart rate.
Type 4 renal tubular acidosis occurs when blood levels of the hormone aldosterone are low or when the kidneys do not respond to it. Aldosterone directs the kidneys to regulate the levels of sodium, potassium, and chloride in the blood. Type 4 renal tubular acidosis also occurs when the tubule transport of electrolytes such as sodium, chloride, and potassium is impaired due to an inherited disorder or the use of certain drugs.
Drugs that may cause type 4 renal tubular acidosis include
- diuretics used to treat congestive heart failure such as spironolactone or eplerenone
- blood pressure drugs called angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs)
- the antibiotic trimethoprim
- the antibiotic pentamidine, which is used to treat pneumonia
- an agent called heparin that keeps blood from clotting
- a class of painkillers called nonsteroidal anti-inflammatory drugs (NSAIDs)
- some immunosuppressive drugs used to prevent rejection.
Type 4 renal tubular acidosis may also result from diseases that alter kidney structure and function such as diabetic nephropathy, HIV/AIDS, Addison’s disease, sickle cell disease, urinary tract obstruction, lupus, amyloidosis, removal or destruction of both adrenal glands, and kidney transplant rejection.
For people who produce aldosterone but cannot use it, researchers have identified the genetic basis for their body’s resistance to the hormone. To treat type 4 renal tubular acidosis successfully, patients may require alkaline agents to correct acidosis and medication to lower the potassium in their blood.
If treated early, most people with any type of renal tubular acidosis will not develop permanent kidney failure. Therefore, the goal is early recognition and adequate therapy, which will need to be maintained and monitored throughout the person’s lifetime.
Table 5. Features of Different Types of Renal Tubular Acidosis
Impaired hydrogen ion excretion
Impaired bicarbonate resorption
Decrease in aldosterone secretion or activity
Plasma bicarbonate (mEq/L)
Frequently <15, occasionally < 10
Usually > 17
Usually low but tends to normalize with alkalinization
Usually low and decreased further by alkalinization
> 7 if plasma bicarbonate is normal
< 5.5 if plasma bicarbonate is depleted (eg, < 15 mEq/L)
What is Fanconi’s syndrome
Fanconi syndrome consists of multiple defects in kidney proximal tubular reabsorption, causing glucosuria (excretion of glucose into the urine), phosphaturia (excessive discharge of phosphates in the urine), generalized aminoaciduria (presence of amino acids in the urine) and bicarbonate wasting 100). It may be hereditary or acquired. Symptoms in children are failure to thrive, growth retardation, and rickets. Symptoms in adults are osteomalacia (softening of the bones) and muscle weakness. Diagnosis is by showing glucosuria, phosphaturia, and aminoaciduria 101). Treatment is sometimes bicarbonate and potassium replacement, removal of offending nephrotoxins (toxic agents or substances that inhibit, damage or destroy the cells and/or tissues of the kidneys), and measures directed at renal failure.
Causes of Fanconi syndrome
Fanconi syndrome can be:
Hereditary Fanconi syndrome
This disorder usually accompanies another genetic disorder, particularly cystinosis 102). Cystinosis is an inherited (autosomal recessive) metabolic disorder in which cystine accumulates within cells and tissues (and is not excreted to excess in the urine as occurs in cystinuria). Besides renal tubular dysfunction, other complications of cystinosis include eye disorders, hepatomegaly, hypothyroidism, and other manifestations.
Fanconi syndrome may also accompany Wilson disease, hereditary fructose intolerance, galactosemia, oculocerebrorenal syndrome (Lowe syndrome), mitochondrial cytopathies, and tyrosinemia. Inheritance patterns vary with the associated disorder.
Acquired Fanconi syndrome
This disorder may be caused by various drugs, including certain cancer chemotherapy drugs (eg, ifosfamide, streptozocin), antiretrovirals (eg, didanosine, cidofovir), and outdated tetracycline 103). All of these drugs are nephrotoxic. Acquired Fanconi syndrome also may occur after renal transplantation and in patients with multiple myeloma, amyloidosis, intoxication with heavy metals or other chemicals, or vitamin D deficiency.
The disordered physiological processes associated with Fanconi syndrome
Various defects of kidney proximal tubular transport function occur, including impaired resorption of glucose, phosphate, amino acids, bicarbonate, uric acid, water, potassium, and sodium. The aminoaciduria is generalized, and, unlike that in cystinuria, increased cystine excretion is a minor component. The basic pathophysiologic abnormality is unknown but may involve a mitochondrial disturbance. Low levels of serum phosphate cause rickets, which is worsened by decreased proximal tubular conversion of vitamin D to its active form.
Symptoms and Signs Fanconi syndrome
In hereditary Fanconi syndrome, the chief clinical features—proximal tubular acidosis, hypophosphatemic rickets, hypokalemia, polyuria, and polydipsia—usually appear in infancy.
When Fanconi syndrome occurs because of cystinosis, failure to thrive and growth retardation are common. The retinas show patchy depigmentation. Interstitial nephritis develops, leading to progressive renal failure that may be fatal before adolescence.
In acquired Fanconi syndrome, adults present with the laboratory abnormalities of renal tubular acidosis (proximal type 2—see Table 2. Features of Different Types of Renal Tubular Acidosis), hypophosphatemia, and hypokalemia. They may present with symptoms of bone disease (osteomalacia) and muscle weakness.
Diagnosis of Fanconi syndrome
- Urine testing for glucose, phosphates, and amino acids.
Diagnosis is made by showing the abnormalities of renal function, particularly glucosuria (in the presence of normal serum glucose), phosphaturia, and aminoaciduria. In cystinosis, slit-lamp examination may show cystine crystals in the cornea.
Treatment of Fanconi syndrome
- Sometimes sodium bicarbonate or potassium bicarbonate or sodium citrate or potassium citrate 104).
- Sometimes potassium supplementation 105).
Other than removing the offending nephrotoxin, there is no specific treatment.
Acidosis may be lessened by giving tablets or solutions of sodium bicarbonate or potassium bicarbonate or sodium citrate or potassium citrate, eg, Shohl’s solution (sodium citrate and citric acid; 1 mL is equivalent to 1 mmol of bicarbonate) given 1 mEq/kg bid to tid or 5 to 15 mL after meals and at bedtime 106).
Potassium depletion may require replacement therapy with a potassium-containing salt.
Hypophosphatemic rickets can be treated.
Kidney transplantation has been successful in treating renal failure. However, when cystinosis is the underlying disease, progressive damage may continue in other organs and eventually result in death 107).
What is Cystinuria
Cystinuria is a condition characterized by the buildup of the amino acid cystine, a building block of most proteins, in the kidneys and bladder. As the kidneys filter blood to create urine, cystine is normally absorbed back into the bloodstream. People with cystinuria cannot properly reabsorb cystine into their bloodstream, so the amino acid accumulates in their urine 108).
As urine becomes more concentrated in the kidneys, the excess cystine forms crystals. Larger crystals become stones that may lodge in the kidneys or in the bladder. Sometimes cystine crystals combine with calcium molecules in the kidneys to form large stones. These crystals and stones can create blockages in the urinary tract and reduce the ability of the kidneys to eliminate waste through urine. The stones also provide sites where bacteria may cause infections. Less than 3% of urinary tract stones are cystine stones 109).
Mutations in the SLC3A1 (type A) or SLC7A9 (type B) gene cause cystinuria 110). The SLC3A1 and SLC7A9 genes provide instructions for making the two parts (subunits) of a protein complex that is primarily found in the kidneys. Normally this protein complex controls the reabsorption of certain amino acids, including cystine, into the blood from the filtered fluid that will become urine. Mutations in either the SLC3A1 gene or SLC7A9 gene disrupt the ability of the protein complex to reabsorb amino acids, which causes the amino acids to become concentrated in the urine 111).
The primary defect results in diminished renal proximal tubular resorption of cystine and as the levels of cystine in the urine increase, the crystals typical of cystinuria form. Cystine is poorly soluble in acidic urine, so when its urinary concentration exceeds its solubility, crystals precipitate and cystine kidney stones form. The other amino acids that are reabsorbed by the protein complex do not create crystals when they accumulate in the urine 112).
Resorption of other dibasic amino acids (lysine, ornithine, arginine) is also impaired but causes no problems because these amino acids have an alternative transport system separate from that shared with cystine 113). Furthermore, they are more soluble than cystine in urine, and their increased excretion does not result in crystal or stone formation. Their absorption (and that of cystine) is also decreased in the small bowel 114).
Cystinuria affects approximately 1 in 10,000 people. Cystine stones are most common in young adults under age 40 115).
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition 116).
Symptoms of Cystinuria
- Blood in the urine
- Renal colic: flank pain or pain in the side or back. Pain is most often on one side; it is rarely felt on both sides. Pain is often severe. It may get worse over days. You may also feel pain in the pelvis, groin, genitals, or between the upper abdomen and back.
- Most commonly renal colic, may occur in infants but usually appear between ages 10 and 30.
- UTI and renal failure due to urinary tract obstruction may develop.
Diagnosis for Cystinuria
The disorder is most often diagnosed after an episode of kidney stones. Testing the stones shows that they are made of cystine.
Unlike calcium-containing stones, cystine stones do not show up well on plain x-rays.
Tests that may be done to detect these stones and diagnose the condition include:
- 24-hour urine collection
- Abdominal CT scan, MRI, or ultrasound
- Intravenous pyelogram (IVP)
- Analysis of collected kidney stones
- Measurement of urinary cystine excretion
Treatment for Cystinuria
The goal of treatment is to relieve symptoms and prevent more stones from forming. A person with severe symptoms may need to go into the hospital.
- drinking plenty of fluids, especially water, to produce large amounts of urine. You should drink at least 6 to 8 glasses per day.
In some cases, fluids may need to be given through a vein (by IV).
End-stage renal disease may develop. Decreasing urinary cystine excretion decreases renal toxicity and is accomplished by increasing urine volume with fluid intake sufficient to provide a urine flow rate of 3 to 4 L/day.
- Hydration is particularly important at night when urinary pH drops.
- Alkalinization of the urine to pH > 7.0 with potassium citrate or potassium bicarbonate 1 mEq/kg po tid to qid and in some cases acetazolamide 5 mg/kg (up to 250 mg) po at bedtime increases the solubility of cystine significantly.
- Mild restrictions of dietary sodium (100 mEq/day) and protein (0.8 to 1.0 g/kg/day) may help reduce cystine excretion.
Medicines may be prescribed to help dissolve the cystine crystals. Eating less salt can also decrease cystine release and stone formation.
You may need pain relievers to control pain in the kidney or bladder area when you pass stones. Smaller stones most often pass through the urine on their own. Larger stones may need extra treatments.
Some large stones may need to be removed with surgery:
- Extracorporeal shock wave lithotripsy (ESWL): Sound waves are passed through the body and are focused on the stones to break them into small, passable fragments. ESWL may not work well for cystine stones because they are very hard as compared with other types of stones.
- Percutaneous nephrostolithotomy or nephrolithotomy: A small tube is placed through the flank directly into the kidney. A telescope is then passed through the tube to fragment the stone under direct vision.
- Ureteroscopy for stones in the lower urinary tract.
Outlook (Prognosis) of Cystinuria
Cystinuria is a chronic, lifelong condition. Stones commonly return. However, the condition rarely results in kidney failure. It does not affect other organs.
Possible Complications of Cystinuria
Complications may include:
- Bladder injury from stone
- Kidney injury from stone
- Kidney infection (pyelonephritis)
- Ureteral obstruction
- Urinary tract infection (UTI)
Prevention of Cystinuria
There are medicines that can be taken so cystine does not form a stone. Ask your doctor about these medicines and their side effects. Any person with a known history of stones in the urinary tract should drink plenty of fluids to regularly produce a high amount of urine. This allows stones and crystals to leave the body before they become large enough to cause symptoms. Decreasing your intake of salt or sodium will help as well.
When high fluid intake and alkalinization do not reduce stone formation, other drugs may be tried.
- Penicillamine (7.5 mg/kg po qid in young children and 125 mg to 0.5 g po qid in older children) improves cystine solubility, but toxicity limits its usefulness. About half of all patients develop some toxic manifestation, such as fever, rash, arthralgias, or, less commonly, nephrotic syndrome, pancytopenia, or SLE-like reaction.
- Pyridoxine supplements (50 mg po once/day) should be given with penicillamine.
- Tiopronin (100 mg to 300 mg po qid) can be used instead of penicillamine to treat some children because it has a lower frequency of adverse effects.
- Captopril (0.3 mg/kg po tid) is not as effective as penicillamine but is less toxic. Close monitoring of response to therapy is very important.
What is Urinary Tract Infections
Urinary tract infections (UTIs) can be divided into upper tract infections, which involve the kidneys (pyelonephritis), and lower tract infections, which involve the bladder (cystitis), urethra (urethritis), and prostate (prostatitis) 117). However, in practice, and particularly in children, differentiating between the sites may be difficult or impossible. Moreover, infection often spreads from one area to the other. Although urethritis and prostatitis are infections that involve the urinary tract, the term urinary tract infection (UTI) usually refers to pyelonephritis (inflammation of the kidney as a result of bacterial infection) and cystitis (inflammation of the urinary bladder, often caused by infection and is usually accompanied by frequent painful urination).
Most cystitis and pyelonephritis are caused by bacteria. The most common nonbacterial pathogens are fungi (usually candidal species), and, less commonly, mycobacteria, viruses, and parasites. Nonbacterial pathogens usually affect patients who are immunocompromised; have diabetes, obstruction, or structural urinary tract abnormalities; or have had recent urinary tract instrumentation.
Other than adenoviruses (implicated in hemorrhagic cystitis), viruses have no major contribution to urinary tract infection (UTI) in immunocompetent patients.
The predominant parasitic causes of urinary tract infections are filariasis, trichomoniasis, leishmaniasis, malaria, and schistosomiasis. Of the parasitic diseases, only trichomoniasis is common in the US, usually as a sexually transmitted disease (STD) 118).
Urethritis is usually caused by an STD 119). Prostatitis is usually caused by a bacterium and is sometimes caused by an STD 120).
Bacterial Urinary Tract Infections
Bacterial UTIs can involve the urethra, prostate, bladder, or kidneys. Symptoms may be absent or include urinary frequency, urgency, dysuria (painful or difficult urination), lower abdominal pain, and flank (the side of a person’s body between the ribs and the hip) pain. Systemic symptoms and even sepsis (chemicals released into the bloodstream to fight the infection trigger inflammatory responses throughout the body) may occur with kidney infection. Diagnosis is based on analysis and culture of urine. Treatment is with antibiotics and removal of any urinary tract catheters and obstructions.
Among adults aged 20 to 50 yr, UTIs are about 50-fold more common in women. In women in this age group, most UTIs are cystitis or pyelonephritis. In men of the same age, most UTIs are urethritis or prostatitis. The incidence of UTI increases in patients > 50 yr, but the female:male ratio decreases because of the increasing frequency of prostate enlargement and instrumentation in men.
The disordered physiological processes associated with Bacterial Urinary Tract Infections
The urinary tract, from the kidneys to the urethral meatus, is normally sterile and resistant to bacterial colonization despite frequent contamination of the distal urethra with colonic bacteria. The major defense against UTI is complete emptying of the bladder during urination. Other mechanisms that maintain the tract’s sterility include urine acidity, vesicoureteral valve, and various immunologic and mucosal barriers.
About 95% of UTIs occur when bacteria ascend the urethra to the bladder and, in the case of pyelonephritis, ascend the ureter to the kidney. The remainder of UTIs are hematogenous. Systemic infection can result from UTI, particularly in the elderly. About 6.5% of cases of hospital-acquired bacteremia are attributable to UTI.
Uncomplicated UTI is usually considered to be cystitis or pyelonephritis that occurs in premenopausal adult women with no structural or functional abnormality of the urinary tract and who are not pregnant and have no significant comorbidity that could lead to more serious outcomes. Also, some experts consider UTIs to be uncomplicated even if they affect postmenopausal women or patients with well-controlled diabetes. In males, most UTIs occur in children or elderly patients, are due to anatomic abnormalities or instrumentation, and are considered complicated.
The rare UTIs that occur in men aged 15 to 50 yr are usually in men who have unprotected anal intercourse or in those who have an uncircumcised penis, and they are generally considered uncomplicated. UTIs in men this age who do not have unprotected anal intercourse or an uncircumcised penis are very rare and, although also considered uncomplicated, warrant evaluation for urologic abnormalities.
Complicated UTI can involve either sex at any age. It is usually considered to be pyelonephritis or cystitis that does not fulfill criteria to be considered uncomplicated. A UTI is considered complicated if the patient is a child, is pregnant, or has any of the following:
- A structural or functional urinary tract abnormality and obstruction of urine flow
- A comorbidity that increases risk of acquiring infection or resistance to treatment, such as poorly controlled diabetes, chronic kidney disease, or immunocompromise.
- Recent instrumentation or surgery of the urinary tract
Risk factors for Bacterial Urinary Tract Infections
Risk factors for development of UTI in women include the following:
- Sexual intercourse
- Diaphragm and spermicide use
- Antibiotic use
- New sex partner within the past year
- History of UTIs in 1st-degree female relatives
- History of recurrent UTIs
- First UTI at early age
Even use of condoms that are spermicide-coated increases risk of UTI in women. The increased risk of UTI in women using antibiotics or spermicides probably occurs because of alterations in vaginal flora that allow overgrowth of Escherichia coli (E.coli). In elderly women, soiling of the perineum due to fecal incontinence increases risk.
Anatomic, structural, and functional abnormalities are risk factors for UTI. A common consequence of anatomic abnormality is vesicoureteral reflux (VUR), which is present in 30 to 45% of young children with symptomatic UTI. VUR is usually caused by a congenital defect that results in incompetence of the ureterovesical valve. VUR can also be acquired in patients with a flaccid bladder due to spinal cord injury or after urinary tract surgery. Other anatomic abnormalities predisposing to UTI include urethral valves (a congenital obstructive abnormality), delayed bladder neck maturation, bladder diverticulum, and urethral duplications.
Structural and functional urinary tract abnormalities that predispose to UTI usually involve obstruction of urine flow and poor bladder emptying. Urine flow can be compromised by calculi and tumors. Bladder emptying can be impaired by neurogenic dysfunction (see Neurogenic Bladder), pregnancy, uterine prolapse, cystocele, and prostatic enlargement. UTI caused by congenital factors manifests most commonly during childhood. Most other risk factors are more common in the elderly.
Other risk factors for UTI include instrumentation (eg, bladder catheterization, stent placement, cystoscopy) and recent surgery.
Causes of Bacterial Urinary Tract Infections
The bacteria that most often cause cystitis and pyelonephritis are the following:
- Enteric (relating to the intestines), usually gram-negative aerobic bacteria (most often)
- Gram-positive bacteria (less often)
In normal genitourinary tracts, strains of Escherichia coli with specific attachment factors for transitional epithelium of the bladder and ureters account for 75 to 95% of cases. The remaining gram-negative urinary pathogens are usually other enterobacteria, typically Klebsiella or Proteus mirabilis, and occasionally Pseudomonas aeruginosa. Among gram-positive bacteria, Staphylococcus saprophyticus is isolated in 5 to 10% of bacterial UTIs. Less common gram-positive bacterial isolates are Enterococcus faecalis (group D streptococci) and Streptococcus agalactiae (group B streptococci), which may be contaminants, particularly if they were isolated from patients with uncomplicated cystitis.
In hospitalized patients, E. coli accounts for about 50% of cases. The gram-negative species Klebsiella, Proteus, Enterobacter, Pseudomonas, and Serratia account for about 40%, and the gram-positive bacterial cocci, E. faecalis, S. saprophyticus, and Staphylococcus aureus account for the remainder.
Classification of Bacterial Urinary Tract Infections
Infection of the urethra with bacteria (or with protozoa, viruses, or fungi) occurs when organisms that gain access to it acutely or chronically colonize the numerous periurethral glands in the bulbous and pendulous portions of the male urethra and in the entire female urethra. The sexually transmitted pathogens Chlamydia trachomatis (Chlamydial, Mycoplasmal, and Ureaplasmal Mucosal Infections), Neisseria gonorrhoeae (Gonorrhea infection), Trichomonas vaginalis (Trichomoniasis), and herpes simplex virus are common causes in both sexes.
Cystitis is infection of the bladder. It is common in women, in whom cases of uncomplicated cystitis are usually preceded by sexual intercourse (honeymoon cystitis). In men, bacterial infection of the bladder is usually complicated and usually results from ascending infection from the urethra or prostate or is secondary to urethral instrumentation. The most common cause of recurrent cystitis in men is chronic bacterial prostatitis.
Acute urethral syndrome
Acute urethral syndrome, which occurs in women, is a syndrome involving dysuria, frequency, and pyuria (dysuria-pyuria syndrome), which thus resembles cystitis. However, in acute urethral syndrome (unlike in cystitis), routine urine cultures are either negative or show colony counts that are lower than the traditional criteria for diagnosis of bacterial cystitis. Urethritis is a possible cause because causative organisms include Chlamydia trachomatis and Ureaplasma urealyticum, which are not detected on routine urine culture.
Noninfectious causes have been proposed, but supporting evidence is not conclusive, and most noninfectious causes usually cause little or no pyuria. Possible noninfectious causes include anatomic abnormalities (eg, urethral stenosis), physiologic abnormalities (eg, pelvic floor muscle dysfunction), hormonal imbalances (eg, atrophic urethritis), localized trauma, gastrointestinal system symptoms, and inflammation.
Asymptomatic bacteriuria is absence of UTI signs or symptoms in a patient whose urine culture satisfies criteria for UTI. Pyuria may or may not be present. Because it is asymptomatic, such bacteriuria is found mainly when high-risk patients are screened or when urine culture is done for other reasons.
Screening patients for asymptomatic bacteriuria is indicated for those at risk of complications if the bacteriuria is untreated. Such patients include:
- Pregnant women at 12 to 16 wks’ gestation or at the first prenatal visit, if later (because of the risk of symptomatic UTI, including pyelonephritis, during pregnancy; and adverse pregnancy outcomes, including low-birth-weight neonate and premature delivery).
- Patients who have had a kidney transplant within the previous 6 months.
- Young children with gross vesicoureteral reflux (the backward flow of urine from the bladder into the kidneys).
- Before certain invasive genitourinary procedures that can cause mucosal bleeding (eg, transurethral resection of the prostate).
Certain patients (eg, postmenopausal women; patients with controlled diabetes; patients with ongoing use of urinary tract foreign objects such as stents, nephrostomy tubes, and indwelling catheters) often have persistent asymptomatic bacteriuria and sometimes pyuria. However, such patients should not be screened because they are at low risk of complicated UTI due to the bacteriuria and thus do not require treatment. Also, in patients with indwelling catheters, treatment often fails to clear the bacteriuria and only leads to development of highly antibiotic-resistant organisms.
Pyelonephritis is bacterial infection of the kidney parenchyma. The term should not be used to describe tubulointerstitial nephropathy unless infection is documented. In women, about 20% of community-acquired bacteremias are due to pyelonephritis. Pyelonephritis is uncommon in men with a normal urinary tract.
In 95% of cases of pyelonephritis, the cause is ascension of bacteria through the urinary tract. Although obstruction (eg, strictures, calculi, tumors, neurogenic bladder, VUR) predisposes to pyelonephritis, most women with pyelonephritis have no demonstrable functional or anatomic defects. In men, pyelonephritis is always due to some functional or anatomic defect. Cystitis alone or anatomic defects may cause reflux. The risk of bacterial ascension is greatly enhanced when ureteral peristalsis is inhibited (eg, during pregnancy, by obstruction, by endotoxins of gram-negative bacteria). Pyelonephritis is common in young girls and in pregnant women after bladder catheterization.
Pyelonephritis not caused by bacterial ascension is caused by hematogenous spread, which is particularly characteristic of virulent organisms such as S. aureus, P. aeruginosa, Salmonella species, and Candida species.
The affected kidney is usually enlarged because of inflammatory PMNs and edema. Infection is focal and patchy, beginning in the pelvis and medulla and extending into the cortex as an enlarging wedge. Cells mediating chronic inflammation appear within a few days, and medullary and subcortical abscesses may develop. Normal parenchymal tissue between foci of infection is common.
Papillary necrosis may be evident in acute pyelonephritis associated with diabetes, obstruction, sickle cell disease, pyelonephritis in renal transplants, pyelonephritis due to candidiasis, or analgesic nephropathy.
Although acute pyelonephritis is frequently associated with renal scarring in children, similar scarring in adults is not detectable in the absence of reflux or obstruction.
Symptoms and Signs of Bacterial Urinary Tract Infections
Elderly patients and patients with a neurogenic bladder or an indwelling catheter may present with sepsis and delirium but without symptoms referable to the urinary tract.
When symptoms are present, they may not correlate with the location of the infection within the urinary tract because there is considerable overlap; however, some generalizations are useful.
In urethritis, the main symptoms are dysuria and, primarily in men, urethral discharge. Discharge can be purulent, whitish, or mucoid. Characteristics of the discharge, such as the amount of purulence, do not reliably differentiate gonococcal from nongonococcal urethritis.
Cystitis onset is usually sudden, typically with frequency, urgency, and burning or painful voiding of small volumes of urine. Nocturia, with suprapubic pain and often low back pain, is common. The urine is often turbid, and microscopic (or rarely gross) hematuria can occur. A low-grade fever may develop. Pneumaturia (passage of air in the urine) can occur when infection results from a vesicoenteric or vesicovaginal fistula or from emphysematous cystitis.
In acute pyelonephritis, symptoms may be the same as those of cystitis. One third of patients have frequency and dysuria. However, with pyelonephritis, symptoms typically include chills, fever, flank pain, colicky abdominal pain, nausea, and vomiting. If abdominal rigidity is absent or slight, a tender, enlarged kidney is sometimes palpable. Costovertebral angle percussion tenderness is generally present on the infected side. In urinary tract infection in children, symptoms often are meager and less characteristic.
Diagnosis of Bacterial Urinary Tract Infections
- Sometimes urine culture
Diagnosis by culture is not always necessary. If done, diagnosis by culture requires demonstration of significant bacteriuria in properly collected urine.
If a sexually transmitted disease (STD) is suspected, a urethral swab for STD testing is obtained prior to voiding. Urine collection is then by clean-catch or catheterization.
To obtain a clean-catch, midstream specimen, the urethral opening is washed with a mild, nonfoaming disinfectant and air dried. Contact of the urinary stream with the mucosa should be minimized by spreading the labia in women and by pulling back the foreskin in uncircumcised men. The first 5 mL of urine is not captured; the next 5 to 10 mL is collected in a sterile container.
A specimen obtained by catheterization is preferable in older women (who typically have difficulty obtaining a clean-catch specimen) and in women with vaginal bleeding or discharge. Many clinicians also use catheterization to obtain a specimen if evaluation includes a pelvic examination. Diagnosis in patients with indwelling catheters is discussed elsewhere (see Catheter-Associated Urinary Tract Infections (CAUTIs) : Diagnosis).
Testing, particularly culturing, should be done within 2 h of specimen collection; if not, the sample should be refrigerated.
Microscopic examination of urine is useful but not definitive. Pyuria is defined as ≥ 8 WBCs/μL of uncentrifuged urine, which corresponds to 2 to 5 WBCs/high-power field in spun sediment. Most truly infected patients have > 10 WBCs/μL. The presence of bacteria in the absence of pyuria, especially when several strains are found, is usually due to contamination during sampling. Microscopic hematuria occurs in up to 50% of patients, but gross hematuria is uncommon. WBC casts, which may require special stains to differentiate from renal tubular casts, indicate only an inflammatory reaction; they can be present in pyelonephritis, glomerulonephritis, and noninfective tubulointerstitial nephritis.
Pyuria in the absence of bacteriuria and of UTI is possible, for example, if patients have nephrolithiasis, a uroepithelial tumor, appendicitis, or inflammatory bowel disease or if the sample is contaminated by vaginal WBCs. Women who have dysuria and pyuria but without significant bacteriuria have the urethral syndrome or dysuria-pyuria syndrome.
Dipstick tests also are commonly used. A positive nitrite test on a freshly voided specimen (bacterial replication in the container renders results unreliable if the specimen is not tested rapidly) is highly specific for UTI, but the test is not very sensitive. The leukocyte esterase test is very specific for the presence of > 10 WBCs/μL and is fairly sensitive. In adult women with uncomplicated UTI with typical symptoms, most clinicians consider positive microscopic and dipstick tests sufficient; in these cases, given the likely pathogens, cultures are unlikely to change treatment but add significant expense.
Cultures are recommended in patients whose characteristics and symptoms suggest complicated UTI or an indication for treatment of bacteriuria. Common examples include the following:
- Pregnant women
- Postmenopausal women
- Prepubertal children
- Patients with urinary tract abnormalities or recent instrumentation
- Patients with immunosuppression or significant comorbidities
- Patients whose symptoms suggest pyelonephritis or sepsis
- Patients with recurrent UTIs (≥ 3/yr)
Samples containing large numbers of epithelial cells are contaminated and unlikely to be helpful. An uncontaminated specimen must be obtained for culture. Culture of a morning specimen is most likely to detect UTI. Samples left at room temperature for > 2 h can give falsely high colony counts due to continuing bacterial proliferation. Criteria for culture positivity include isolation of a single bacterial species from a midstream, clean catch, or catheterized urine specimen.
For asymptomatic bacteriuria, criteria for culture positivity based on the guidelines of the Infectious Diseases Society of America are:
- Two consecutive clean-catch, voided specimens (for men, one specimen) from which the same bacterial strain is isolated in colony counts of >105/mL
- Among women or men, in a catheter-obtained specimen, a single bacterial species is isolated in colony counts of > 102/mL
For symptomatic patients, culture criteria are:
- Uncomplicated cystitis in women: > 103/mL
- Uncomplicated cystitis in women: > 102/mL (This quantification may be considered to improve sensitivity to E. coli.)
- Acute, uncomplicated pyelonephritis in women: > 104/mL
- Complicated UTI: > 105/mL in women; or > 104/mL in men or from a catheter-derived specimen in women
- Acute urethral syndrome: > 102/mL of a single bacterial species
Any positive culture result, regardless of colony count, in a sample obtained via suprapubic bladder puncture should be considered a true positive.
In midstream urine, E. coliin mixed flora may be a true pathogen 121).
Occasionally, UTI is present despite lower colony counts, possibly because of prior antibiotic therapy, very dilute urine (specific gravity < 1.003), or obstruction to the flow of grossly infected urine. Repeating the culture improves the diagnostic accuracy of a positive result, ie, may differentiate between a contaminant and a true positive result.
Clinical differentiation between upper and lower UTI is impossible in many patients, and testing is not usually advisable. When the patient has high fever, costovertebral angle tenderness, and gross pyuria with casts, pyelonephritis is highly likely. The best noninvasive technique for differentiating bladder from kidney infection appears to be the response to a short course of antibiotic therapy. If the urine has not cleared after 3 days of treatment, pyelonephritis should be sought.
Symptoms similar to those of cystitis and urethritis can occur in patients with vaginitis, which may cause dysuria due to the passage of urine across inflamed labia. Vaginitis can often be distinguished by the presence of vaginal discharge, vaginal odor, and dyspareunia.
Seriously ill patients require evaluation for sepsis, typically with complete blood count, electrolytes, lactate, blood urea nitrogen (BUN – test measures the amount of nitrogen in your blood that comes from the waste product urea), creatinine, and blood cultures. Patients with abdominal pain or tenderness are evaluated for other causes of an acute abdomen.
Patients who have dysuria/pyuria but no bacteriuria should have testing for an STD, typically using nucleic acid-based testing of swabs from the urethra and cervix.
Most adults do not require assessment for structural abnormalities unless the following occur:
- The patient has ≥ 2 episodes of pyelonephritis.
- Infections are complicated.
- Nephrolithiasis is suspected.
- There is painless gross hematuria or new renal insufficiency.
- Fever persists for ≥ 72 h.
Urinary tract imaging choices include ultrasonography, CT, and IVU. Occasionally, voiding cystourethrography, retrograde urethrography, or cystoscopy is warranted. Urologic investigation is not routinely needed in women with symptomatic cystitis or asymptomatic recurrent cystitis, because findings do not influence therapy. Children with UTI often require imaging.
Treatment of Bacterial Urinary Tract Infections
Occasionally surgery (eg, to drain abscesses, correct underlying structural abnormalities, or relieve obstruction)
All forms of symptomatic bacterial UTI require antibiotics. For patients with troublesome dysuria, phenazopyridine may help control symptoms until the antibiotics do (usually within 48 h).
Choice of antibiotic should be based on the patient’s allergy and adherence history, local resistance patterns (if known), antibiotic availability and cost, and patient and provider tolerance for risk of treatment failure. Propensity for inducing antibiotic resistance should also be considered. When urine culture is done, choice of antibiotic should be modified when culture and sensitivity results are available to the most narrow-spectrum drug effective against the identified pathogen.
Surgical correction is usually required for obstructive uropathy, anatomic abnormalities, and neuropathic urinary tract lesions such as compression of the spinal cord. Catheter drainage of an obstructed urinary tract aids in prompt control of UTI. Occasionally, a renal cortical abscess or perinephric abscess requires surgical drainage. Instrumentation of the lower urinary tract in the presence of infected urine should be deferred if possible. Sterilization of the urine before instrumentation and antibiotic therapy for 3 to 7 days after instrumentation can prevent life-threatening urosepsis.
Sexually active patients with symptoms are usually treated presumptively for STDs pending test results. A typical regimen is ceftriaxone 250 mg IM plus either azithromycin 1 g orally once or doxycycline 100 mg po bid for 7 days. All sex partners within 60 days should be evaluated. Men diagnosed with urethritis should be tested for HIV and syphilis in accordance with the Centers for Disease Control and Prevention’s 2015 Sexually Transmitted Diseases Treatment Guidelines.
First-line treatment of uncomplicated cystitis is nitrofurantoin 100 mg po bid for 5 days (it is contraindicated if creatinine clearance is < 60 mL/min), trimethoprim/sulfamethoxazole 160/800 mg orally twice daily for 3 days, or fosfomycin 3 g orally once. Less desirable choices include a fluoroquinolone or a beta-lactam antibiotic. If cystitis recurs within a week or two, a broader spectrum antibiotic (eg, a fluoroquinolone) can be used and the urine should be cultured.
Complicated cystitis should be treated with empiric broad-spectrum antibiotics chosen based on local pathogens and resistance patterns and adjusted based on culture results. Urinary tract abnormalities must also be managed.
Acute urethral syndrome
Treatment depends on clinical findings and urine culture results:
- Women with dysuria, pyuria, and colony growth of > 102/mL of a single bacterial species on urine culture can be treated as for uncomplicated cystitis.
- Women who have dysuria and pyuria with no bacteriuria should be evaluated for an STD (including for N. gonorrhoeae and C. trachomatis).
- Women who have dysuria but neither pyuria nor bacteriuria do not have the true urethral syndrome. They should be evaluated for noninfectious causes of dysuria. Evaluation may include therapeutic trials, for example, of behavioral treatments (eg, biofeedback and pelvic musculature relaxation), surgery (for urethral stenosis), and drugs (eg, hormone replacement for suspected atrophic urethritis, anesthetics, antispasmodics).
Typically, asymptomatic bacteriuria in patients with diabetes, elderly patients, or patients with chronically indwelling bladder catheters should not be treated. However, patients at risk of complications from asymptomatic bacteriuria (see Asymptomatic bacteriuria) should have any treatable causes addressed and be given antibiotics as for cystitis. In pregnant women, only a few antibiotics can be safely used. Oral beta-lactams, sulfonamides, and nitrofurantoin are considered safe in early pregnancy, but trimethoprim should be avoided during the 1st trimester, and sulfamethoxazole should be avoided during the 3rd trimester, particularly near parturition. Patients with untreatable obstructive problems (eg, calculi, reflux) may require long-term suppressive therapy.
Antibiotics are required. Outpatient treatment with oral antibiotics is possible if all of the following criteria are satisfied:
- Patients are expected to be adherent
- Patients are immunocompetent
- Patients have no nausea or vomiting or evidence of volume depletion or septicemia
- Patients have no factors suggesting complicated UTI
Ciprofloxacin 500 mg po bid for 7 days and levofloxacin 750 mg po once/day for 5 days are 1st-line antibiotics if < 10% of the uropathogens in the community are resistant. A 2nd option is usually trimethoprim/sulfamethoxazole 160/800 mg orally twice per day for 14 days. However, local sensitivity patterns should be considered because in some parts of the US, > 20% of E. coli are resistant to sulfa.
Patients not eligible for outpatient treatment should be hospitalized and given parenteral therapy selected on the basis of local sensitivity patterns. First-line antibiotics are usually renally excreted fluoroquinolones, such as ciprofloxacin and levofloxacin. Other choices, such as ampicillin plus gentamicin, broad-spectrum cephalosporins (eg, ceftriaxone, cefotaxime, cefepime), aztreonam, beta-lactam/beta-lactam inhibitor combinations (ampicillin/sulbactam, ticarcillin/clavulanate, piperacillin/tazobactam), and imipenem/cilastatin, are usually reserved for patients with more complicated pyelonephritis (eg, with obstruction, calculi, resistant bacteria, or a hospital-acquired infection) or recent urinary tract instrumentation.
Parenteral therapy is continued until defervescence and other signs of clinical improvement occur. In > 80% of patients, improvement occurs within 72 h. Oral therapy can then begin, and the patient can be discharged for the remainder of a 7- to14-day treatment course. Complicated cases require longer courses of IV antibiotics with total duration of 2 to 3 wk and urologic correction of anatomic defects.
Outpatient management can be considered in pregnant women with pyelonephritis, but only if symptoms are mild, close follow-up is available, and (preferably) pregnancy is < 24 wk gestation. Outpatient treatment is with cephalosporins (eg, ceftriaxone 1 to 2 g IV or IM, then cephalexin 500 mg po qid for 10 days). Otherwise, 1st-line IV antibiotics include cephalosporins, aztreonam, or ampicillin plus gentamicin. If pyelonephritis is severe, possibilities include piperacillin/tazobactam or meropenem. Fluoroquinolones and trimethoprim/sulfamethoxazole should be avoided. Because recurrence is common, some authorities recommend prophylaxis after the acute infection resolves with nitrofurantoin 100 mg orally or cephalexin 250 mg orally every night during the remainder of the pregnancy and for 4 to 6 wk after pregnancy.
Prevention of Bacterial Urinary Tract Infections
In women who experience ≥ 3 UTIs/yr, behavioral measures are recommended, including increasing fluid intake, avoiding spermicides and diaphragm use, not delaying urination, wiping front to back after defecation, avoiding douching, and urinating immediately after sexual intercourse. Although some evidence shows that cranberry products prevent UTI in women, others do not; the optimal dose is unknown; and they can have high amounts of oxalates (possibly increasing risk of oxalate stones). Thus, most experts do not recommend use of cranberry products for prevention of symptomatic UTI in women.
If these techniques are unsuccessful, antibiotic prophylaxis should be considered. Common options are continuous and postcoital prophylaxis.
Continuous prophylaxis commonly begins with a 6 mo trial. If UTI recurs after 6 mo of prophylactic therapy, prophylaxis may be reinstituted for 2 or 3 yr. Choice of antibiotic depends on susceptibility patterns of prior infections. Common options are trimethoprim/sulfamethoxazole 40/200 mg orally once/day or 3 times per week, nitrofurantoin 50 or 100 mg orally once/day, cephalexin 125 to 250 mg orally once/day, and fosfomycin 3 g po q 10 days. Fluoroquinolones are effective but are not usually recommended because resistance is increasing. Also, fluoroquinolones are contraindicated in pregnant women and children. Nitrofurantoin is contraindicated if creatinine clearance is < 60 mL/min. Long-term use can rarely cause damage to the lungs, liver, and nervous system.
Postcoital prophylaxis in women may be more effective if UTIs are temporally related to sexual intercourse. Usually, a single dose of one of the drugs used for continuous prophylaxis (other than fosfomycin) is effective.
Contraception is recommended for women using a fluoroquinolone because these drugs can potentially injure a fetus. Although concern exists that antibiotics may decrease the effectiveness of oral contraceptives, pharmacokinetic studies have not shown a significant or consistent effect. Nonetheless, some experts still recommend that women who use oral contraceptives use barrier contraceptives while they are taking antibiotics.
In pregnant women, effective prophylaxis of UTI is similar to that in nonpregnant women, including use of postcoital prophylaxis. Appropriate patients include those with acute pyelonephritis during a pregnancy, patients with > 1 episode (despite treatment) of UTI or bacteriuria during pregnancy, and patients who required prophylaxis for recurrent UTI before pregnancy.
In postmenopausal women, antibiotic prophylaxis is similar to that described previously. Additionally, topical estrogen therapy markedly reduces the incidence of recurrent UTI in women with atrophic vaginitis or atrophic urethritis.
What are Cystic Kidney diseases
A cyst is a fluid-filled sac. You may get simple kidney cysts as you age; they are usually harmless. There are also some diseases which cause kidney cysts. One type is polycystic kidney disease (PKD). It runs in families. In polycystic kidney disease, many cysts grow in the kidneys. This can enlarge the kidneys and make them work poorly. About half of people with the most common type of polycystic kidney disease end up with kidney failure. Polycystic kidney disease also causes cysts in other parts of the body, such as the liver.
Often, there are no symptoms at first. Later, symptoms include
- Pain in the back and lower sides
- Blood in the urine
Doctors diagnose polycystic kidney disease with imaging tests and family history. There is no cure. Treatments can help with symptoms and complications. They include medicines and lifestyle changes, and if there is kidney failure, dialysis or kidney transplants.
Figure 4. Polycystic Kidney Disease
What are the differences between acquired cystic kidney disease and polycystic kidney disease ?
Acquired cystic kidney disease differs from polycystic kidney disease in several ways. Unlike acquired cystic kidney disease, polycystic kidney disease is a genetic, or inherited, disorder that can cause complications such as high blood pressure and problems with blood vessels in the brain and heart.
The following lists the differences:
People with Polycystic Kidney Disease
- are born with a gene that causes the disease
- have enlarged kidneys
- develop cysts in the liver and other parts of the body.
People with Acquired Cystic Kidney Disease
- do not have a disease-causing gene
- have kidneys that are normal-sized or smaller
- do not form cysts in other parts of the body.
In addition, for people with polycystic kidney disease, the presence of cysts marks the onset of their disease, while people with acquired cystic kidney disease already have chronic kidney disease when they develop cysts.
What is Polycystic Kidney Disease ?
Polycystic kidney disease is is a genetic disorder that causes many fluid-filled cysts to grow in your kidneys and other organs. Clusters of fluid-filled sacs, called cysts, develop in the kidneys and interfere with their ability to filter waste products from the blood. Unlike the usually harmless simple kidney cysts that can form in the kidneys later in life, polycystic kidney disease cysts can change the shape of your kidneys, including making them much larger 122). The growth of cysts causes the kidneys to become enlarged and can lead to kidney failure. Cysts may also develop in other organs, particularly the liver.
Polycystic kidney disease is a fairly common genetic disorder. It affects about 500,000 people in the United States 123). The autosomal dominant form of the disease is much more common than the autosomal recessive form. Autosomal dominant polycystic kidney disease affects 1 in 500 to 1,000 people, while the autosomal recessive type occurs in an estimated 1 in 20,000 to 40,000 people 124).
Polycystic kidney disease also can cause other complications, or problems, such as dangerously high blood pressure, pain in the back or sides, blood in the urine (hematuria), recurrent urinary tract infections, kidney stones, and heart valve abnormalities, cysts in the liver and problems with blood vessels in your brain and heart 125). Additionally, people with polycystic kidney disease have an increased risk of an abnormal bulging (an aneurysm) in a large blood vessel called the aorta or in blood vessels at the base of the brain. Aneurysms can be life-threatening if they tear or rupture 126).
Polycystic kidney disease is associated with the following conditions:
- Aortic aneurysms
- Brain aneurysms
- Cysts in the liver, pancreas, and testes
- Diverticula of the colon
As many as half of people with polycystic kidney disease have cysts in the liver 127).
Polycystic kidney disease is a form of chronic kidney disease that reduces kidney function and may lead to kidney failure.
The two major forms of polycystic kidney disease are distinguished by the usual age of onset and the pattern in which it is passed through families. The autosomal dominant form (sometimes called Autosomal Dominant Polycystic kidney disease or ADPKD) has signs and symptoms that typically begin in adulthood, although cysts in the kidney are often present from birth or childhood. Autosomal dominant polycystic kidney disease can be further divided into type 1 and type 2, depending on the genetic cause. The autosomal recessive form of polycystic kidney disease (sometimes called Autosomal Recessive Polycystic kidney disease or ARPKD) is much rarer and is often lethal early in life. The signs and symptoms of this condition are usually apparent at birth or in early infancy.
What causes Polycystic kidney disease ?
A gene mutation, or defect, causes polycystic kidney disease. In most polycystic kidney disease cases, a child got the gene mutation from a parent. In a small number of polycystic kidney disease cases, the gene mutation developed on its own, without either parent carrying a copy of the mutated gene. This type of mutation is called “spontaneous.”
The two main types of polycystic kidney disease are:
- Autosomal Dominant Polycystic kidney disease (ADPKD), which is usually diagnosed in adulthood
- Autosomal Recessive Polycystic kidney disease (ARPKD), which can be diagnosed in the womb or shortly after a baby is born.
Inheritance Pattern and Genetic Changes of Polycystic kidney disease
Mutations in the PKD1, PKD2, and PKHD1 genes cause polycystic kidney disease 128).
Mutations in either the PKD1 or PKD2 gene can cause autosomal dominant polycystic kidney disease; PKD1 gene mutations cause Autosomal Dominant Polycystic kidney disease (ADPKD) type 1, and PKD2 gene mutations cause Autosomal Dominant Polycystic kidney disease (ADPKD) type 2 129). These genes provide instructions for making proteins whose functions are not fully understood. Researchers believe that they are involved in transmitting chemical signals from outside the cell to the cell’s nucleus. The two proteins work together to promote normal kidney development, organization, and function. Mutations in the PKD1 or PKD2 gene lead to the formation of thousands of cysts, which disrupt the normal functions of the kidneys and other organs 130). People with mutations in the PKD2 gene, particularly women, typically have a less severe form of the disease than people with PKD1 mutations 131). The signs and symptoms, including a decline in kidney function, tend to appear later in adulthood in people with a PKD2 mutation.
Mutations in the PKHD1 gene cause autosomal recessive polycystic kidney disease 132). This gene provides instructions for making a protein whose exact function is unknown; however, the protein likely transmits chemical signals from outside the cell to the cell nucleus. Researchers have not determined how mutations in the PKHD1 gene lead to the formation of numerous cysts characteristic of polycystic kidney disease.
Although polycystic kidney disease is usually a genetic disorder, a small percentage of cases are not caused by gene mutations 133). These cases are called acquired polycystic kidney disease. This form of the disorder occurs most often in people with other types of kidney disease who have been treated for several years with hemodialysis (a procedure that filters waste products from the blood).
Most cases of polycystic kidney disease have an autosomal dominant pattern of inheritance 134). People with this condition are born with one mutated copy of the PKD1 or PKD2 gene in each cell. In about 90 percent of these cases, an affected person inherits the mutation from one affected parent. The other 10 percent of cases result from a new mutation in one of the genes and occur in people with no history of the disorder in their family.
Although one altered copy of a gene in each cell is sufficient to cause the disorder, an additional mutation in the second copy of the PKD1 or PKD2 gene may make cysts grow faster and increase the severity of the disease 135). The rate at which cysts enlarge and cause a loss of kidney function varies widely, and may be influenced by mutations in other genes that have not been identified.
Polycystic kidney disease also can be inherited in an autosomal recessive pattern. People with this form of the condition have two altered copies of the PKHD1 gene in each cell. The parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.
How common is Polycystic kidney disease ?
Polycystic kidney disease is one of the most common genetic disorders. Polycystic kidney disease affects about 500,000 people in the United States.
ADPKD affects 1 in every 400 to 1,000 people in the world, and Autosomal Recessive Polycystic kidney disease (ARPKD) affects 1 in 20,000 children 136), 137).
Who is more likely to have Polycystic kidney disease ?
Polycystic kidney disease affects people of all ages, races, and ethnicities worldwide. The disorder occurs equally in women and men.
What are the signs and symptoms of Polycystic kidney disease ?
The signs and symptoms of Autosomal Dominant Polycystic kidney disease (ADPKD), such as pain, high blood pressure, and kidney failure, are also polycystic kidney disease complications. In many cases, Autosomal Dominant Polycystic kidney disease (ADPKD) does not cause signs or symptoms until your kidney cysts are a half inch or larger in size.
Early signs of Autosomal Recessive Polycystic kidney disease (ARPKD) in the womb are larger-than-normal kidneys and a smaller-than-average size baby, a condition called growth failure. The early signs of Autosomal Recessive Polycystic kidney disease (ARPKD) are also complications. However, some people with Autosomal Recessive Polycystic kidney disease (ARPKD) do not develop signs or symptoms until later in childhood or even adulthood.
Symptoms of polycystic kidney disease may include any of the following:
- Abdominal pain or tenderness
- Blood in the urine
- Excessive urination at night
- Flank pain on one or both sides
- Joint pain
- Nail abnormalities
Diagnosis of Polycystic kidney disease
An examination may show:
- Abdominal tenderness over the liver
- Enlarged liver
- Heart murmurs or other signs of aortic insufficiency or mitral insufficiency
- High blood pressure
- Growths in the kidneys or abdomen
Tests that may be done include:
- Cerebral angiography
- Complete blood count (CBC) to check for anemia
- Liver tests (blood)
People with a personal or family history of polycystic kidney disease who have headaches should be tested to determine if cerebral aneurysms are the cause.
Polycystic kidney disease and cysts on the liver or other organs may be found using the following tests:
- Abdominal CT scan
- Abdominal MRI scan
- Abdominal ultrasound
- Intravenous pyelogram (IVP)
If several members of your family have polycystic kidney disease, genetic tests can be done to determine whether you carry the polycystic kidney disease gene.
Can you prevent polycystic kidney disease ?
Researchers have not yet found a way to prevent polycystic kidney disease. However, you may be able to slow polycystic kidney disease problems caused by high blood pressure, such as kidney damage. Aim for a blood pressure goal of less than 120/80. Work with a health care team to help manage your or your child’s polycystic kidney disease. The health care team will probably include a general practitioner and a nephrologist, a health care provider specializing in kidney health.
What can you do to slow down polycystic kidney disease ?
The sooner you know you or your child has polycystic kidney disease, the sooner you can keep the condition from getting worse. Getting tested if you or your child are at risk for polycystic kidney disease can help you take early action.
Make lifestyle changes To Slow Down Polycystic Kidney Disease
- Be active for 30 minutes or more on most days. Regular physical activity can help you reduce stress, manage your weight, and control your blood pressure. If you are not active now, ask your health care provider about how much and what type of physical activity is right for you.
If you play contact sports, such as football or hockey, a health care provider should do a magnetic resonance imaging (MRI) test to see whether these sports are safe for you. Trauma to your body, especially to your back and sides, may cause kidney cysts to burst.
- Lose weight. Being overweight makes your kidneys work harder. Losing weight helps protect your kidneys.
- Aim for 7 to 8 hours of sleep each night. Getting enough sleep is important to your overall physical and mental health and can help you manage your blood pressure and blood glucose, or blood sugar.
- Reduce stress. Long-term stress can raise your blood pressure and even lead to depression. Some of the steps you take to manage your polycystic kidney disease are also healthy ways to cope with stress. For example, getting enough physical activity and sleep helps reduce stress.
- Quit smoking. Cigarette smoking can raise your blood pressure, making your kidney damage worse. Quitting smoking may help you meet your blood pressure goals, which is good for your kidneys and can lower your chances of having a heart attack or stroke. Quitting smoking is even more important for people with polycystic kidney disease who have aneurysms. An aneurysm is a bulge in the wall of a blood vessel. For tips on quitting, go to Smokefree.gov
- Change what you eat and drink. You may need to change what you eat and drink to help control your blood pressure and protect your kidneys. People with any kind of kidney disease, including polycystic kidney disease, should talk with a dietitian about which foods and drinks to include in their healthy eating plan and which may be harmful. Staying hydrated by drinking the right amount of fluid may help slow polycystic kidney disease’s progress toward kidney failure. Read more about what to eat or drink if you have polycystic kidney disease or are at risk for polycystic kidney disease.
Treatment of polycystic kidney disease
Currently, no treatment can prevent the cysts from forming or enlarging 138).
The goal of treatment is to control symptoms and prevent complications. Treatment may include:
- Blood pressure medicines. Two types of blood pressure medicines, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), may slow kidney disease and delay kidney failure.
- Diuretics (water pills)
- Low-salt diet
Any urinary tract infection should be treated quickly with antibiotics.
Cysts that are painful, infected, bleeding, or causing a blockage may need to be drained. There are usually too many cysts to make it practical to remove each cyst.
Surgery to remove 1 or both kidneys may be needed. Treatments for end-stage kidney disease may include dialysis or a kidney transplant.
Outlook (Prognosis) for polycystic kidney disease
The disease gets worse slowly. Eventually, it may lead to end-stage kidney failure. It is also associated with liver disease, including infection of liver cysts.
Treatment may relieve symptoms for many years.
People with polycystic kidney disease who don’t have other diseases may be good candidates for a kidney transplant.
Possible Complications of polycystic kidney disease
Health problems that may result from polycystic kidney disease include:
- Bleeding or rupture of cysts
- Chronic kidney disease
- End-stage kidney disease
- High blood pressure
- Infection of liver cysts
- Kidney stones
- Liver failure (mild to severe)
- Repeated urinary tract infections
What is acquired cystic kidney disease ?
Acquired cystic kidney disease (ACKD) happens in people who have chronic kidney disease, especially if they are on dialysis. Unlike polycystic kidney disease, the kidneys are normal sized, and cysts do not form in other parts of the body. Acquired cystic kidney disease often has no symptoms. Usually, the cysts are harmless and do not need treatment. If they do cause complications, treatments include medicines, draining the cysts, or surgery.
Acquired cystic kidney disease occurs in children and adults who have:
- Chronic kidney disease (CKD)—a condition that develops over many years and may lead to end-stage kidney disease. The kidneys of people with CKD gradually lose their ability to filter wastes, extra salt, and fluid from the blood properly.
- End-stage kidney disease (ESRD) is the last stage (stage five) of chronic kidney disease (CKD). When CKD, polycystic kidney disease (PKD) or other kidney diseases develop into end-stage kidney disease, blood-filtering treatments called dialysis or a kidney transplant is necessary to live.
The cysts are more likely to develop in people who are on kidney dialysis. The chance of developing acquired cystic kidney disease increases with the number of years a person is on dialysis. However, the cysts are caused by chronic kidney disease or kidney failure, not dialysis treatments.
How common is acquired cystic kidney disease ?
Acquired cystic kidney disease becomes more common the longer a person has chronic kidney disease.
- About 7 to 22 percent of people with chronic kidney disease already have acquired cystic kidney disease before starting dialysis treatments.
- Almost 60 percent of people on dialysis for 2 to 4 years develop acquired cystic kidney disease 139).
- About 90 percent of people on dialysis for 8 years develop acquired cystic kidney disease 140).
What causes acquired cystic kidney disease ?
Researchers do not fully understand what causes cysts to grow in the kidneys of people with chronic kidney disease. The fact that these cysts occur only in the kidneys and not in other parts of the body, as in polycystic kidney disease, indicates that the processes that lead to cyst formation take place primarily inside the kidneys 141).
What are the signs and symptoms of acquired cystic kidney disease ?
A person with acquired cystic kidney disease often has no symptoms. However, the complications of acquired cystic kidney disease can have signs and symptoms.
What are the complications of acquired cystic kidney disease ?
People with acquired cystic kidney disease may develop the following complications:
- an infected cyst, which can cause fever and back pain.
- blood in the urine, which can signal that a cyst in the kidney is bleeding.
- tumors in the kidneys. People with acquired cystic kidney disease are more likely than people in the general population to have cancerous kidney tumors. However, the chance of cancer spreading is lower in people with acquired cystic kidney disease than that of other kidney cancers not associated with acquired cystic kidney disease, and the long-term outlook is better 142).
How is acquired cystic kidney disease diagnosed ?
A doctor may diagnose a person with acquired cystic kidney disease based on
- medical history
- imaging tests
Taking a medical history may help a health care provider diagnose acquired cystic kidney disease. A health care provider may suspect acquired cystic kidney disease if a person who has been on dialysis for several years develops symptoms such as fever, back pain, or blood in the urine.
To confirm the diagnosis, the health care provider may order one or more imaging tests. A radiologist—a doctor who specializes in medical imaging—interprets the images from these tests, and the patient does not need anesthesia.
- Ultrasound uses a device, called a transducer, that bounces safe, painless sound waves off organs to create an image of their structure. A specially trained technician performs the procedure in a health care provider’s office, an outpatient center, or a hospital. The images can show cysts in the kidneys as well as the kidneys’ size and shape.
- Computerized tomography (CT) scans use a combination of x-rays and computer technology to create images. For a CT scan, a nurse or technician may give the patient a solution to drink and an injection of a special dye, called contrast medium. CT scans require the patient to lie on a table that slides into a tunnel-shaped device where an x-ray technician takes the x-rays. An x-ray technician performs the procedure in an outpatient center or a hospital. CT scans can show cysts and tumors in the kidneys.
- Magnetic resonance imaging (MRI) is a test that takes pictures of the body’s internal organs and soft tissues without using x-rays. A specially trained technician performs the procedure in an outpatient center or a hospital. Although the patient does not need anesthesia, a health care provider may give people with a fear of confined spaces light sedation, taken by mouth. An MRI may include the injection of contrast medium. With most MRI machines, the patient will lie on a table that slides into a tunnel-shaped device that may be open-ended or closed at one end. Some machines allow the patient to lie in a more open space. During an MRI, the patient, although usually awake, must remain perfectly still while the technician takes the images, which usually takes only a few minutes. The technician will take a sequence of images from different angles to create a detailed picture of the kidneys. During the test, the patient will hear loud mechanical knocking and humming noises from the machine.
Sometimes a doctor may discover acquired cystic kidney disease during an imaging exam for another condition. Images of the kidneys may help the doctor distinguish acquired cystic kidney disease from polycystic kidney disease.
How is acquired cystic kidney disease treated ?
If acquired cystic kidney disease is not causing complications, a person does not need treatment. A health care provider will treat infections with antibiotics—medications that kill bacteria. If large cysts are causing pain, a health care provider may drain the cyst using a long needle inserted into the cyst through the skin.
When a surgeon transplants a new kidney into a patient’s body to treat kidney failure, acquired cystic kidney disease in the damaged kidneys, which usually remain in place after a transplant, often disappears.
A surgeon may perform an operation to remove tumors or suspected tumors. In rare cases, a surgeon performs an operation to stop cysts from bleeding.
Eating, Diet, and Nutrition for Acquired Cystic Kidney Disease
No specific diet will prevent or delay acquired cystic kidney disease. In general, a diet designed for people on hemodialysis or peritoneal dialysis reduces the amount of wastes that accumulate in the body between dialysis sessions.
- Eating & Nutrition for Hemodialysis
Hemodialysis removes extra fluid from your body. However, hemodialysis can remove only so much fluid at a time safely. If you come to your hemodialysis with too much fluid in your body, your treatment may make you feel ill. You may get muscle cramps or have a sudden drop in blood pressure that causes you to feel dizzy or sick to your stomach.
Your choices about what to eat and drink while on hemodialysis can make a difference in how you feel and can make your treatments work better.
Between dialysis treatment sessions, wastes can build up in your blood and make you sick. You can reduce waste buildup by controlling what you eat and drink.
You can match what you eat and drink with what your kidney treatments remove.
Some foods cause wastes to build up quickly between your dialysis sessions. If your blood contains too much waste, your kidney treatment session may not remove them all.
What is my dry weight ?
Your dry weight is your weight after a hemodialysis session has removed all extra fluid from your body. Controlling your liquid intake helps you stay at your proper dry weight. If you let too much fluid build up between sessions, it is harder to achieve your dry weight. Your health care provider can help you figure out what dry weight is right for you.
My dry weight goal: _____________
What you should eat and drink while on hemodialysis
You will need to carefully plan your meals and keep track of the amount of liquids you eat and drink. It helps to limit or avoid foods and beverages that have lots of:
- sodium—for example, vegetable juice and sports drinks.
Your dialysis center has a renal dietitian to help you plan your meals. A renal dietitian has special training in caring for the food and nutrition needs of people with kidney disease.
Use this information to help you learn how to eat right to feel right on hemodialysis. Read one section at a time.
Keep a copy of this information handy to remind yourself of foods you can eat and foods to avoid.
What you need to know about potassium
Healthy kidneys keep the right amount of potassium in your blood to keep your heart beating at a steady pace. Potassium levels can rise between hemodialysis sessions and affect your heartbeat. Eating too much potassium can be dangerous to your heart and may even cause death.
To control potassium levels, limit potassium-rich foods such as avocados, bananas, kiwis, and dried fruit. Choose fruits and vegetables that are lower in potassium. Have very small portions of foods that are higher in potassium, such as one or two cherry tomatoes on a salad or a few raisins in your oatmeal.
You can remove some of the potassium from potatoes by dicing or shredding them and then boiling them in a full pot of water.
To remove some of the potassium from potatoes:
- Dice potatoes into small pieces.
- Or, grate potatoes into shreds.
- And then boil potatoes in a full pot of water.
Your renal dietitian will give you more specific information about the potassium content of foods.
What you need to know about phosphorus
Too much phosphorus in your blood pulls calcium from your bones. Losing calcium may make your bones weak and likely to break. Also, too much phosphorus may make your skin itch. Limiting phosphorus can be hard because foods that contain phosphorus, such as meat and milk, also contain the protein you need. You should be careful to eat enough protein; however, not so much that you get too much phosphorus. Processed and packaged foods contain especially high levels of phosphorus. You can also find phosphorus naturally in foods such as poultry, fish, nuts, peanut butter, beans, cola, tea, and dairy products. Usually, people on hemodialysis should only have a 1/2 cup of milk per day.
Your renal dietitian will give you more specific information about phosphorus.
You may need to take a phosphate binder such as sevelamer (Renvela), calcium acetate (PhosLo), lanthanum carbonate (Fosrenol), or calcium carbonate to control the phosphorus in your blood between hemodialysis sessions. These medicines, the phosphorus binder “seals” the phosphorus from food and moves it out through stool so the phosphorous does not enter the bloodstream.
What you need to know about protein
Renal dietitians encourage most people on hemodialysis to eat high-quality protein because it produces less waste for removal during dialysis. High-quality protein comes from meat, poultry, fish, and eggs. Avoid processed meats such as hot dogs and canned chili, which have high amounts of sodium and phosphorus.
What you need to know about sodium
Sodium is a part of salt. Sodium is found in many canned, packaged, frozen, and fast foods. Sodium is also found in many condiments, seasonings, and meats. Too much sodium makes you thirsty, which makes you drink more liquid.
Try to eat fresh, naturally low-sodium foods. Look for products labeled “low sodium,” especially in canned and frozen foods.
Do not use salt substitutes because they contain potassium. Talk with your renal dietitian about spices you can use to flavor your food. Your renal dietitian can help you find spice blends without sodium or potassium.
What you need to know about calories
All foods contain calories, and you need calories for energy. Many people on hemodialysis do not have a good appetite and do not get enough calories. If you find you do not feel like eating, talk with your renal dietitian to find healthy ways to add calories to your diet. Vegetable oils—such as olive oil, canola oil, and safflower oil—are good sources of calories and are the healthiest way to add fat to your diet if you need to gain weight. Use them generously on breads, rice, and noodles only if your renal dietitian tells you to add calories to your diet.
Butter and margarines are rich in calories; however, they are mainly saturated fat. Saturated fats and trans fats can clog your arteries. Use them less often. Soft margarine that comes in a tub is better than stick margarine. Choose a soft margarine with less saturated and trans fats.
Talk with your renal dietitian about the types and amounts of fat you need in your diet. Everyone will have different needs that a renal dietitian can help address.
Hard candy, sugar, honey, jam, and jelly provide calories and energy without fat or adding other things that your body does not need. If you have diabetes, be careful about eating sweets and talk with your renal dietitian before adding sweets to your food plan.
Should you take vitamin and mineral supplements ?
Do not take nutritional supplements you can buy over the counter. These supplements may contain vitamins or minerals that are harmful to you. For safety reasons, talk with your health care provider before using probiotics, dietary supplements, or any other medicine together with or in place of the treatment your health care provider prescribes.
Why is it important to keep track of how much liquid you eat or drink ?
You may feel better if you keep track of and limit how much liquid you eat and drink. Excess fluid can build up in your body and may cause
- swelling and weight gain between dialysis sessions
- changes in your blood pressure
- your heart to work harder, which can lead to serious heart trouble
- a buildup of fluid in your lungs, making it hard for you to breathe
Your health care provider can help you figure out how much liquid is right for you.
One way to limit how much liquid you have is to limit the salt in the foods you eat. Salt makes you thirsty, so you drink more. Avoid salty foods such as chips and pretzels.
Your renal dietitian will give you other tips to help you limit how much liquid you consume while making sure you don’t feel too thirsty.
What foods count as liquid and why ?
Foods that are liquid at room temperature, such as soup, contain water. Gelatin, pudding, ice cream, and other foods that include a lot of liquid in the recipe also count. Most fruits and vegetables contain water, such as melons, grapes, apples, oranges, tomatoes, lettuce, and celery. When you count up how much liquid you have in a day, be sure to count these foods.
Nutrition for Advanced Chronic Kidney Disease in Adults
A person may prevent or delay some health problems from chronic kidney disease by eating the right foods and avoiding foods high in sodium, potassium, and phosphorus 143). Learning about calories, fats, proteins, and fluids is important for a person with advanced chronic kidney disease. Protein foods such as meat and dairy products break down into waste products that healthy kidneys remove from the blood.
As chronic kidney disease progresses, nutritional needs change. A health care provider may recommend that a patient with reduced kidney function choose foods carefully.
Chronic kidney disease usually takes a long time to develop and does not go away. In chronic kidney disease, the kidneys continue to work—just not as well as they should. Wastes may build up so gradually that the body becomes used to having those wastes in the blood. Salts containing phosphorus and potassium may rise to unsafe levels, causing heart and bone problems. Anemia—low red blood cell count—can result from chronic kidney disease because the kidneys stop making enough erythropoietin, a hormone that causes bone marrow to make red blood cells. After months or years, chronic kidney disease may progress to permanent kidney failure, which requires a person to have a kidney transplant or regular blood filtering treatments called dialysis.
What is medical nutrition therapy (MNT) ?
Medical nutrition therapy is the use of nutrition counseling by a registered dietitian to help promote a medical or health goal. A health care provider may refer a patient to a registered dietitian to help with the patient’s food plan. Many insurance policies cover medical nutrition therapy when recommended by a health care provider. Anyone who qualifies for Medicare can receive a benefit for medical nutrition therapy from a registered dietitian or nutrition professional when a health care provider provides a referral indicating that the person has diabetes or kidney disease.
One way to locate a qualified dietitian is to contact the Academy of Nutrition and Dietetics at www.eatright.org and click on “Find a Registered Dietitian.” Users can enter their address or ZIP code for a list of dietitians in their area. A person looking for dietary advice to prevent kidney damage should click on “Renal (Kidney) Nutrition” in the specialty field. Dietitians who specialize in helping people with chronic kidney disease are called renal dietitians.
Why is knowing about calories important for someone with advanced chronic kidney disease ?
As chronic kidney disease progresses, people often lose their appetites because they find that foods do not taste the same. As a result, they consume fewer calories—important units of energy in food—and may lose too much weight. Renal dietitians can help people with advanced chronic kidney disease find healthy ways to add calories to their diet if they are losing too much weight.
Why is knowing about protein important for someone with advanced chronic kidney disease ?
Protein is an essential part of any diet. Proteins help build and maintain muscle, bone, skin, connective tissue, internal organs, and blood. They help fight disease and heal wounds. But proteins also break down into waste products that must be removed from the blood by the kidneys. Eating more protein than the body needs may put an extra burden on the kidneys and cause kidney function to decline faster.
Health care providers recommend that people with chronic kidney disease eat moderate or reduced amounts of protein. However, restricting protein could lead to malnutrition, so people with chronic kidney disease need to be careful. The typical American diet contains more than enough protein. Learning about portion sizes can help people limit protein intake without endangering their health.
What is the right meat portion size ?
Most people—with or without chronic kidney disease—can get the daily protein they need by eating two 3-ounce servings of meat or meat substitute. A 3-ounce serving of meat is about the size of a deck of cards or the palm of a person’s hand.
A renal dietitian can help people learn about the amount and sources of protein in their diet. Animal protein in egg whites, cheese, chicken, fish, and red meats contain more of the essential nutrients a body needs. With careful meal planning, a well-balanced vegetarian diet can also provide these nutrients. A renal dietitian can help people with advanced chronic kidney disease make small adjustments in their eating habits that can result in significant protein reduction. For example, people can lower their protein intake by making sandwiches using thinner slices of meat and adding lettuce, cucumber slices, apple slices, and other garnishes. The following table lists some higher-protein foods and suggestions for lower-protein alternatives that are better choices for people with chronic kidney disease trying to limit their protein intake.
When kidney function declines to the point where dialysis becomes necessary, patients should include more protein in their diet because dialysis removes large amounts of protein from the blood.
Why is knowing about fat important for someone with advanced chronic kidney disease ?
Everyone should know about fat sources because eating the wrong kinds of fat and too much fat increases the risk of clogged blood vessels and heart problems. Fat provides energy, helps produce hormonelike substances that regulate blood pressure and other heart functions, and carries fat-soluble vitamins. Everyone needs dietary fat, but some fats are healthier than others. People with chronic kidney disease are at higher risk of having a heart attack or stroke. Therefore, people with chronic kidney disease should be especially careful about how dietary fat affects their heart health.
People with advanced chronic kidney disease should talk with a dietitian about healthy and unhealthy sources of fat. Saturated fats and trans-fatty acids can raise blood cholesterol levels and clog blood vessels. Saturated fats are found in animal products such as red meat, poultry, whole milk, and butter. These fats are usually solid at room temperature. Trans-fatty acids are often found in commercially baked goods such as cookies and cakes and in fried foods like doughnuts and french fries.
A dietitian can suggest healthy ways to include fat in the diet, especially if more calories are needed. Vegetable oils such as corn or safflower oil are healthier than animal fats such as butter or lard. Hydrogenated vegetable oils should be avoided because they are high in trans-fatty acids. Monounsaturated fats—olive, peanut, and canola oils—are healthy alternatives to animal fats. The table below shows the sources of fats, broken down into three types of fats that should be eaten less often and good fats that can be eaten more often.
Why is knowing about sodium important for someone with advanced chronic kidney disease ?
Too much sodium in a person’s diet can be harmful because it causes blood to hold fluid. People with chronic kidney disease need to be careful not to let too much fluid build up in their bodies. The extra fluid raises blood pressure and puts a strain on the heart and kidneys. A dietitian can help people find ways to reduce the amount of sodium in their diet. Nutrition labels provide information about the sodium content in food. The U.S. Food and Drug Administration advises that healthy people should limit their daily sodium intake to no more than 2,300 milligrams (mg), the amount found in 1 teaspoon of table salt. People who are at risk for a heart attack or stroke because of a condition such as high blood pressure or kidney disease should limit their daily sodium intake to no more than 1,500 mg. Choosing sodium-free or low-sodium food products will help them reach that goal.
Sodium is found in ordinary table salt and many salty seasonings such as soy sauce and teriyaki sauce. Canned foods, some frozen foods, and most processed meats have large amounts of salt. Snack foods such as chips and crackers are also high in salt.
Alternative seasonings such as lemon juice, salt-free seasoning mixes, and hot pepper sauce can help people reduce their salt intake. People with advanced chronic kidney disease should avoid salt substitutes that use potassium, such as AlsoSalt or Nu-Salt, because chronic kidney disease limits the body’s ability to eliminate potassium from the blood.
Why is knowing about potassium important for someone with advanced chronic kidney disease ?
Keeping the proper level of potassium in the blood is essential. Potassium keeps the heart beating regularly and muscles working right. Problems can occur when blood potassium levels are either too low or too high. Damaged kidneys allow potassium to build up in the blood, causing serious heart problems. Potassium is found in many fruits and vegetables, such as bananas, potatoes, avocados, and melons. People with advanced chronic kidney disease may need to avoid some fruits and vegetables. Blood tests can indicate when potassium levels have climbed above normal range. A renal dietitian can help people with advanced chronic kidney disease find ways to limit the amount of potassium they eat. The potassium content of potatoes and other vegetables can be reduced by boiling them in water. The following table gives examples of some high-potassium foods and suggestions for low-potassium alternatives for people with advanced chronic kidney disease.
Why is knowing about phosphorus important for someone with advanced chronic kidney disease ?
Damaged kidneys allow phosphorus, a mineral found in many foods, to build up in the blood. Too much phosphorus in the blood pulls calcium from the bones, making the bones weak and likely to break. Too much phosphorus may also make skin itch. Foods such as milk and cheese, dried beans, peas, colas, canned iced teas and lemonade, nuts, and peanut butter are high in phosphorus. A renal dietitian can help people with advanced chronic kidney disease learn how to limit phosphorus in their diet.
As chronic kidney disease progresses, a person may need to take a phosphate binder such as sevelamer hydrochloride (Renagel), lanthanum carbonate (Fosrenol), calcium acetate (PhosLo), or calcium carbonate (Tums) to control the phosphorus in the blood. These medications act like sponges to soak up, or bind, phosphorus while it is in the stomach. Because it is bound, the phosphorus does not get into the blood. Instead, it is removed from the body in the stool.
Why is regulating fluid intake important for someone with advanced chronic kidney disease ?
People with advanced chronic kidney disease may need to limit how much they drink because damaged kidneys can’t remove extra fluid. The fluid builds up in the body and strains the heart. Patients should tell their health care provider about any swelling around the eyes or in the legs, arms, or abdomen.
Is there kidney stone home remedy
Due to the complex and multifactoral causes of kidney stones that involve many diseases that may include urinary tract infections, sexually transmitted disease, hypercalciuria, hyperparathyroidism, cystinuria, hypocitruria, sarcoidosis, bone metastases, multiple myeloma, solitary kidney, urinary tract anomalies, renal tubular acidosis, hyperuricosuria, etc., there is no home remedy available to get rid of kidney stone safely and prevent long term kidney stone complications. Recovery and analysis of the kidney stone, measurement of kidney stone-forming substances in the urine, and the clinical tests (e.g. blood tests, kidney function tests, 24 hour urine test, CT scan, etc.) are needed to plan proper kidney stone diagnosis, management, prevention and treatment. Complications of kidney stones like infections, chronic kidney disease and end-stage kidney disease where you’ll need a kidney transplant are rare if you seek treatment from a health care professional before these problems occur. Therefore we do not recommend any home remedy.
However there are general measures you can do to prevent recurrent kidney stone formation:
- Low urine volume is the most common abnormality and the single most important preventable factor to correct so as to avoid kidney stone recurrences. The only home remedy would be to drink large amounts of water— to achieve a urine volume of at least 2.5 liters daily to prevent kidney stone from forming. People who have had cystine stones may need to drink even more. The amount of fluid each person needs to drink depends on the weather and the person’s activity level—people who work or exercise in hot weather need more fluid to replace the fluid they lose through sweat. A 24-hour urine
collection may be used to determine the volume of urine produced during a day. If the volume of urine produced is too low, the person can be advised to increase fluid intake. Drinking enough fluid is the most important thing a person can do to prevent kidney stones.
- Risk of a recurrent stone is about 50% within five to seven years 144).
- Diets low in salt (< 1500 mg/day) and animal proteins (< 52 g/day) are helpful in decreasing the frequency of recurrent calcium oxalate stones 145).
- Decrease intake of animal protein (≤ 52 g/day): Reduces production of metabolic acids, resulting in a lower level of acid induced calcium excretion; increases excretion of citrate that forms a soluble complex with calcium; and reduces supersaturation with respect to calcium oxalate and limits the excretion of uric acid 146). Meats and other animal protein—such as eggs and fish—contain purines, which break down into uric acid in the urine. Foods especially rich in purines include organ meats, such as liver. People who form uric acid stones should limit their meat consumption to 6 ounces each day. Animal protein may also raise the risk of calcium stones by increasing the excretion of calcium and reducing the excretion of citrate into the urine. Citrate prevents kidney stones, but the acid in animal protein reduces the citrate in urine.
- Restrict salt intake (< 1500 mg/day of sodium chloride): Dietary and urinary sodium is directly correlated with urinary calcium excretion, and lower urinary excretion of sodium reduces urinary calcium excretion 147). Sodium, often from salt, causes the kidneys to excrete more calcium into the urine. High concentrations of calcium in the urine combine with oxalate and phosphorus to form stones. Reducing sodium intake is preferred to reducing calcium intake. The risk of kidney stones increases with increased daily sodium consumption. People who form calcium oxalate or calcium phosphate stones should limit their intake to the American Heart Association level, even if they take medications to prevent kidney stones.
- Normal calcium intake (≥ 800 mg/day): Low calcium diets increase urinary oxalate excretion, which may result in more stone formation and possibly a negative calcium balance 148). Calcium from food does not increase the risk of calcium oxalate stones. Calcium in the digestive tract binds to oxalate from food and keeps it from entering the blood, and then the urinary tract, where it can form stones. People who form calcium oxalate stones should include 800 mg of calcium in their diet every day, not only for kidney stone prevention but also to maintain bone density. A cup of low-fat milk contains 300 mg of calcium. Other dairy products such as yogurt are also high in calcium. For people who have lactose intolerance and must avoid dairy products, orange juice fortified with calcium or dairy with reduced lactose content may be alternatives. Calcium supplements may increase the risk of calcium oxalate stones if they are not taken with food. Some studies suggest citrus drinks like lemonade and orange juice protect against kidney stones because they contain citrate, which stops crystals from growing into stones. But watch for the added sugar and extra calories from the citrus drinks which can lead to weight gain and obesity. Studies have shown that being overweight increases the risk of kidney stones, particularly uric acid stones.
- Decrease dietary oxalate: Reduce the intake of foods rich in oxalate—spinach, rhubarb, chocolate, nuts and wheat bran 149). Some of the oxalate in urine is made by the body. However, eating certain foods with high levels of oxalate can increase the amount of oxalate in the urine, where it combines with calcium to form calcium oxalate stones. Foods that have been shown to increase the amount of oxalate in urine include — spinach, rhubarb, nuts, chocolate and wheat bran. Avoiding these foods may help reduce the amount of oxalate in the urine.
- Cranberry juice: Decreases oxalate and phosphate excretion and increases citrate excretion 150). Cranberry juice has antilithogenic properties and, as such, deserves consideration as a conservative therapeutic protocol in managing calcium oxalate urolithiasis.
- Studies have shown the Dietary Approaches to Stop Hypertension (DASH) diet can reduce the risk of kidney stones. The DASH diet is high in fruits and vegetables, moderate in low-fat dairy products, and low in animal protein. More information about the DASH diet can be found here What is the DASH Diet ?
Does the type of kidney stone you have affect food choices you should make ?
Yes. If you have already had kidney stones, ask your health care professional which type of kidney stone you had. Based on the type of kidney stone you had, you may be able to prevent kidney stones by making changes in how much sodium, animal protein, calcium, or oxalate is in the food you eat.
You may need to change what you eat and drink for these types of kidney stones:
- Calcium Oxalate Stones
- Calcium Phosphate Stones
- Uric Acid Stones
- Cystine Stones
A dietitian who specializes in kidney stone prevention can help you plan meals to prevent kidney stones. Find a dietitian who can help you.
Calcium Oxalate Stones
If you’ve had calcium oxalate stones, you may want to avoid these foods to help reduce the amount of oxalate in your urine:
- nuts and nut products
- peanuts—which are legumes, not nuts, and are high in oxalate
- wheat bran
Talk with a health care professional about other food sources of oxalate and how much oxalate should be in what you eat.
Your chance of developing kidney stones increases when you eat more sodium. Sodium is a part of salt. Sodium is in many canned, packaged, and fast foods. It is also in many condiments, seasonings, and meats.
Talk with a health care professional about how much sodium should be in what you eat.
Tips to Reduce Your Sodium Intake
Most Americans consume too much sodium. Adults should aim to consume less than 2,300 mg a day. One teaspoon of table salt has 2,325 milligrams (mg) of sodium. If you have had calcium oxalate or calcium phosphate stones, you should follow this guideline, even if you take medicine to prevent kidney stones.
Here are some tips to help you reduce your sodium intake:
- Check the Percent Daily Value (%DV) for sodium on the Nutrition Facts label found on many foods. Low in sodium is 5% or less, and high in sodium is 20% or more.
- Consider writing down how much sodium you consume each day.
- When eating out, ask about the sodium content in the food.
- Cook from scratch. Avoid processed and fast foods, canned soups and vegetables, and lunch meats.
- Look for foods labeled: sodium free, salt free, very low sodium, low sodium, reduced or less sodium, light in sodium, no salt added, unsalted, and lightly salted.
Check labels for ingredients and hidden sodium, such as:
- sodium bicarbonate, the chemical name for baking soda
- baking powder, which contains sodium bicarbonate and other chemicals
- disodium phosphate
- monosodium glutamate, or MSG
- sodium alginate
- sodium nitrate or nitrite
Limit animal protein
Eating animal protein may increase your chances of developing kidney stones.
A health care professional may tell you to limit eating animal protein, including:
- beef, chicken, and pork, especially organ meats
- fish and shellfish
- milk, cheese, and other dairy products
Although you may need to limit how much animal protein you eat each day, you still need to make sure you get enough protein. Consider replacing some of the meat and animal protein you would typically eat with beans, dried peas, and lentils, which are plant-based foods that are high in protein and low in oxalate.
Talk with a health care professional about how much total protein you should eat and how much should come from animal or plant-based foods.
Get enough calcium from foods
Even though calcium sounds like it would be the cause of calcium stones, it’s not. In the right amounts, calcium can block other substances in the digestive tract that may cause stones. Talk with a health care professional about how much calcium you should eat to help prevent getting more calcium oxalate stones and to support strong bones. It may be best to get calcium from low-oxalate, plant-based foods such as calcium-fortified juices, cereals, breads, some kinds of vegetables, and some types of beans. Ask a dietitian or other health care professional which foods are the best sources of calcium for you.
Calcium Phosphate Stones
Your chance of developing kidney stones increases when you eat more sodium. Sodium is a part of salt. Sodium is in many canned, packaged, and fast foods. It is also in many condiments, seasonings, and meats.
Talk with a health care professional about how much sodium should be in what you eat.
Limit animal protein
Eating animal protein may increase your chances of developing kidney stones.
A health care professional may tell you to limit eating animal protein, including:
- beef, chicken, and pork, especially organ meats
- fish and shellfish
- milk, cheese, and other dairy products
Although you may need to limit how much animal protein you have each day, you still need to make sure you get enough protein. Consider replacing some of the meat and animal protein you would typically eat with some of these plant-based foods that are high in protein:
- legumes such as beans, dried peas, lentils, and peanuts
- soy foods, such as soy milk, soy nut butter, and tofu
- nuts and nut products, such as almonds and almond butter, cashews and cashew butter, walnuts, and pistachios
- sunflower seeds
Talk with a health care professional about how much total protein you should eat and how much should come from animal or plant-based foods.
Get enough calcium from foods
Even though calcium sounds like it would be the cause of calcium stones, it’s not. In the right amounts, calcium can block other substances in the digestive tract that may lead to stones. Talk with a health care professional about how much calcium you should eat to help prevent getting more calcium phosphate stones and to support strong bones. It may be best to get calcium from plant-based foods such as calcium-fortified juices, cereals, breads, some kinds of vegetables, and some types of beans. Ask a dietitian or other health care professional which foods are the best sources of calcium for you.
Uric Acid Stones
Limit animal protein
Eating animal protein may increase your chances of developing kidney stones.
A health care professional may tell you to limit eating animal protein, including
- beef, chicken, and pork, especially organ meats
- fish and shellfish
- milk, cheese, and other dairy products
Although you may need to limit how much animal protein you have each day, you still need to make sure you get enough protein. Consider replacing some of the meat and animal protein you would typically eat with some of these plant-based foods that are high in protein:
- legumes such as beans, dried peas, lentils, and peanuts
- soy foods, such as soy milk, soy nut butter, and tofu
- nuts and nut products, such as almonds and almond butter, cashews and cashew butter, walnuts, and pistachios
- sunflower seeds
Talk with a health care professional about how much total protein you should eat and how much should come from animal or plant-based foods.
Losing weight if you are overweight is especially important for people who have had uric acid stones.
Drinking enough liquid, mainly water, is the most important lifestyle change you can make to prevent cystine stones. Talk with a health care professional about how much liquid you should drink.
Kidney stones formation now appear to be related to chronic conditions that require long-term medical management, dietary and lifestyle changes and sometimes drug therapy and/or surgery. Kidney stones are a risk factor for chronic kidney disease and progression to end-stage renal disease 151). Persons with kidney stones are more likely to have traditional risk factors for chronic kidney disease (e.g., hypertension, preexisting kidney disease, diabetes, proteinuria, albuminuria), as well as non-traditional factors (e.g., interstitial nephritis, chronic pyelonephritis, female sex) 152).
A family history of kidney stones (increases your risk by three times), insulin resistant states, a history of hypertension, primary hyperparathyroidism, a history of gout, chronic metabolic acidosis, and surgical menopause are all associated with increased risk of kidney stones 153). Incidence of stones is higher in patients with an anatomical abnormality of the urinary tract that may result in urinary stasis. Most patients (up to 80%) with calcium stones have one or more of the metabolic risk factors and about 25% of stones are idiopathic in origin. Various drugs can also increase your risk of kidney stone disease.
Your kidneys remove waste from your blood by filtering the blood and making urine. Kidney stones formation are complex and involves many diseases that may include urinary tract infections (eg, hypercalciuria, urinary tract infections, hyperparathyroidism, cystinuria, hypocitruria, sarcoidosis, bone metastases, multiple myeloma, solitary kidney, urinary tract anomalies, renal tubular acidosis, hyperuricosuria, etc.) that will require medical diagnosis, treatment and management. Incidence of kidney stones is higher in patients with an anatomical abnormality of the urinary tract that may result in urinary stasis. Complications of kidney stones are rare if you seek treatment from a health care professional before problems occur.
- Kidney stones can form when substances in the urine—such as calcium, oxalate, and phosphorus— become highly concentrated. Diet is one of several factors that can promote or inhibit kidney stone formation.
- Four major types of kidney stones can form: calcium stones, uric acid stones, struvite stones, and cystine stones.
- Drinking enough fluids — that will achieve a urine volume of at least 2.5 liters daily— is the most important thing a person can do to prevent all kidney stones 154)).
- Sodium, often from salt, causes the kidneys to excrete more calcium into the urine. High concentrations of calcium in the urine combine with oxalate and phosphorus to form stones. Reducing sodium intake (to less than 1500 mg per day) is preferred to reducing calcium intake.
- Meats and other animal protein—such as eggs and fish—contain purines, which break down into uric acid in the urine.
- Calcium from food does not increase the risk of calcium oxalate stones. Calcium in the digestive tract binds to oxalate from food and keeps it from entering the blood, and then the urinary tract, where it can form stones.
Kidney stones may remain within the kidney or renal collecting system or be passed into the ureter and bladder. During passage, the stones may irritate the ureter and may become lodged, obstructing urine flow and causing hydroureter and sometimes hydronephrosis.
Even partial obstruction causes decreased glomerular filtration (renal function), which may persist briefly after the calculus has passed. With hydronephrosis and elevated glomerular pressure, renal blood flow declines, further worsening renal function. Generally, however, in the absence of infection, permanent renal dysfunction occurs only after about 28 days of complete obstruction.
Secondary infection can occur with long-standing obstruction, but most patients with calcium-containing calculi do not have infected urine.
Therefore, if you suspect that you may have kidney stone or have symptoms of urinary tract stones, see your health care provider ASAP to prevent permanent kidney damage. Recovery and analysis of the kidney stone, measurement of kidney stone-forming substances in the urine, and the clinical history are needed to plan proper kidney stone diagnosis, management, prevention and treatment.
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