What is blind loop syndrome

Blind loop syndrome occurs when part of the small intestine becomes bypassed as a complication of abdominal surgery or as a consequence of gastrointestinal disorders which impede effective motility ¹⁾. Digested food slows or stops moving through part of the small intestines (blind loop). This causes bacteria to grow too much in a portion of the small intestine that is unintentionally bypassed and leads to problems in absorbing nutrients.

Sometimes called stasis syndrome or stagnant loop syndrome, blind loop syndrome is often a complication of stomach (abdominal) surgery. But blind loop syndrome can also result from structural problems and some diseases. Sometimes surgery is needed to correct the problem, but antibiotics are the most common treatment.

Figure 1. Blind loop

Clinical signs of blind loop syndrome include bloating, abdominal pain, diarrhea and weight loss. If untreated, the clinical course progresses to malabsorption of fats, vitamin B12 and calcium, the latter which predisposes to nephrolithiasis (kidney stones) and osteoporosis ²⁾.

Outlook (Prognosis) for blind loop syndrome

Many patients get better with antibiotics. If surgical repair is needed, the outcome is usually very good.

Blind loop syndrome causes

The small intestine is the longest section of your digestive tract, measuring about 20 feet (6.1 meters). The small intestine is where food mixes with digestive juices and nutrients are absorbed into your bloodstream.

Unlike your large intestine (colon), your small intestine normally has relatively few bacteria.

The name of this condition refers to the “blind loop” formed by the bypassed small intestine. This blind loop does not allow digested food to flow normally through the intestinal tract.

In the blind loop syndrome, stagnant food in the bypassed small intestine becomes an ideal breeding ground for bacteria. The bacteria may produce toxins as well as block the absorption of nutrients.

The greater the length of small bowel involved in the blind loop, the greater the chance of bacterial overgrowth.

When a section of the small intestine is affected by blind loop syndrome, the bile salts needed to digest fats become ineffective. This leads to fatty stools and poor absorption of fat and fat-soluble vitamins. Vitamin B12 deficiency may occur because the extra bacteria that develop in this situation use up all of the vitamin.

Blind loop syndrome is a complication that occurs:

• After many operations, including subtotal gastrectomy (surgical removal of part of the stomach) to treat peptic ulcers and stomach cancer and including gastric bypass operations for extreme obesity
• As a complication of inflammatory bowel disease
• Structural problems in and around your small intestine, including scar tissue (intestinal adhesions) on the outside of the bowel and small, bulging pouches of tissue that protrude through the intestinal wall (diverticulosis)
• Certain medical conditions, including Crohn’s disease, radiation enteritis, scleroderma, celiac disease, obesity and diabetes, can slow movement (motility) of food and waste products through the small intestine

Diseases such as diabetes or scleroderma may slow down movement in a segment of the intestine, leading to blind loop syndrome.

Risk factors of blind loop syndrome

Factors that increase your risk of blind loop syndrome include:

• Gastric surgery for obesity or ulcers
• A structural defect in the small intestine
• An injury to the small intestine
• An abnormal passageway (fistula) between two segments of bowel
• Crohn’s disease, intestinal lymphoma or scleroderma involving the small intestine
• History of radiation therapy to the abdomen
• Diabetes
• Diverticulosis of the small intestine

Possible Complications of Blind loop syndrome

• Complete intestinal obstruction
• Death of intestine (intestinal infarction)
• Hole (perforation) in intestine
• Malabsorption and malnutrition
  • Poor absorption of fats. Bacteria in your small intestine break down the bile salts needed to digest fats. As a result, your body can’t fully absorb the fat-soluble vitamins A, D, E and K. Incomplete absorption of fats leads to diarrhea, weight loss and vitamin deficiency disorders.
  • Vitamin B-12 deficiency. Bacteria in the small intestine absorb vitamin B-12, which is essential for the normal functioning of your nervous system and the production of blood cells and DNA. A severe B-12 deficiency can lead to weakness, fatigue, tingling and numbness in your hands and feet, and, in advanced cases, to mental confusion. Damage to your central nervous system resulting from a B-12 deficiency may be irreversible.
• Brittle bones (osteoporosis). Over time, damage to your intestine from abnormal bacterial growth causes poor calcium absorption, and eventually may lead to bone diseases, such as osteoporosis.
• Kidney stones. Poor calcium absorption may also eventually result in kidney stones.
• Damage to the intestinal lining. Toxins that are released when bacteria break down stagnant food harm the mucous lining (mucosa) of the small intestine. As a result, most nutrients, including carbohydrates and proteins, are poorly absorbed, leading to serious malnourishment.

Blind loop syndrome symptoms

Signs and symptoms of blind loop syndrome often include:

• Loss of appetite
• Abdominal pain
• Nausea
• Bloating
• An uncomfortable feeling of fullness after eating
• Diarrhea
• Unintentional weight loss
• Fatty stools
• Fullness after a meal
• Unintentional weight loss

Blind loop syndrome diagnosis

During a physical examination, the doctor may notice a mass in, or swelling of, the abdomen.

The first step in diagnosing blind loop syndrome is usually an imaging test, such as:

• Abdominal X-ray
• Abdominal CT scan

You may have additional tests to check for bacterial overgrowth in your small intestine, poor fat absorption, or other problems that may be causing or contributing to your symptoms:

• Barium X-ray of the small intestine. This test uses a contrast solution (barium) to coat the lining of your intestine so that it stands out clearly on X-rays. A barium X-ray may reveal a blind loop, diverticulosis, a narrowing (stricture) of the intestine or other structural problems, as well as slow transit times that can cause bacterial overgrowth.
• CT enterography. This test is more sensitive than is a barium X-ray or conventional CT. It helps detect inflammation or structural problems in the bowel and abnormalities in other organs, such as the pancreas.
• Hydrogen breath test. This test measures the amount of hydrogen that you breathe out after drinking a mixture of glucose and water. A rapid rise in hydrogen indicates poor carbohydrate digestion and bacterial overgrowth in your small intestine. Although widely available, this test is less sensitive than other breath tests.
• D-xylose breath test. This test, which is more accurate than a hydrogen breath test, measures the amount of carbon dioxide in your breath. High levels of carbon dioxide suggest bacterial overgrowth.
• Bile acid breath test. Bile acids from your liver help digest fats (lipids) in your small intestine. Bacterial overgrowth interferes with the process. This test uses a bile salt with a radioactive tracer to check for bile salt dysfunction.
• Quantitative fecal fat test. This test can determine how well your small intestine absorbs fat. You eat a high-fat diet for three days, and the amount of fat in your stool is then measured. Large amounts of undigested fat may be caused by bacterial overgrowth, but more commonly result from other conditions such as short bowel syndrome or chronic pancreatitis.
• Small intestine aspirate and fluid culture. This is the most sensitive test for bacterial overgrowth. To obtain the fluid sample, doctors pass a long, flexible tube (endoscope) down your throat and through your upper digestive tract to your small intestine. A sample of intestinal fluid is withdrawn and then tested in a laboratory for the growth of bacteria.

If your doctor believes that bacterial overgrowth is very likely, he or she may begin treatment with antibiotics immediately without specific testing.

Blind loop syndrome treatment

Whenever possible, doctors treat blind loop syndrome by dealing with the underlying problem — for example, by surgically repairing a postoperative blind loop, stricture or fistula. But the blind loop can’t always be reversed. In that case, treatment focuses on correcting nutritional deficiencies and eliminating bacterial overgrowth.

Treatment generally starts with antibiotics for the excess bacteria growth, along with vitamin B12 supplements. If antibiotics don’t work, surgery to help the food flow through the intestine may be considered.

Antibiotic therapy

For most people, the initial way to treat bacterial overgrowth is with antibiotics. Doctors may start this treatment if your symptoms and medical history strongly suggest this is the cause, even when test results are inconclusive or without any testing at all. Testing may be performed if antibiotic treatment is not effective.

A short course of antibiotics often significantly reduces the number of abnormal bacteria. But bacteria can return when the antibiotic is discontinued, so treatment may need to be long term. Some people with a blind loop may go for long periods without needing antibiotics, while others may need them regularly.

Doctors may also switch among different antibiotics to help prevent bacterial resistance. Antibiotics wipe out most intestinal bacteria, both normal and abnormal. As a result, antibiotics can cause some of the very problems they’re trying to cure, including diarrhea. Switching among different drugs can help avoid this problem.

Nutritional support

Correcting nutritional deficiencies is a crucial part of treating blind loop syndrome, particularly in people with severe weight loss. Malnutrition can be treated, but the damage it causes can’t always be reversed.

These treatments may improve vitamin deficiencies, reduce intestinal distress and help with weight gain:

• Nutritional supplements. People with blind loop syndrome may need intramuscular injections of vitamin B-12, as well as oral vitamins, calcium and iron supplements.
• Lactose-free diet. Damage to the small intestine may cause you to lose the ability to digest milk sugar (lactose). In that case, it’s important to avoid most lactose-containing products, or use lactase preparations that help digest milk sugar.

Some people may tolerate yogurt because the bacteria used in the culturing process naturally break down lactose.

• Medium-chain triglycerides. Most dietary fats consist of a long chain of fat molecules (triglycerides). Some people with blind loop syndrome have an easier time digesting medium-chain triglycerides, found in coconut oil.

Medium-chain triglycerides are sometimes prescribed as a dietary supplement for people with severe blind loop syndrome resulting in short bowel syndrome.