What is a virtual colonoscopy

Virtual colonoscopy is also called CT (computerized tomography) colonography, is a procedure in which a radiologist uses x-rays and a computer to create images of your rectum and colon from outside the body. Virtual colonoscopy can show ulcers, polyps, and cancer.

The x-rays are painless. Pumping air into the colon may cause cramping or gas pains.

After the ct colonography exam:

• You may feel bloated and have mild abdominal cramping and pass a lot of gas.
• You should be able to return to your regular activities.

Why do doctors use virtual colonoscopy?

Virtual colonoscopy may be done for the following reasons:

• Follow-up on colon cancer or polyps
• Abdominal pain, changes in bowel movements, or weight loss
• Anemia due to low iron
• Blood in the stool or black, tarry stools
• Screen for cancer of the colon or rectum (should be done every 5 years)

Doctors mainly use virtual colonoscopy to screen for polyps or cancer. Screening may find diseases at an early stage, when a doctor has a better chance of curing the disease.

Your doctor may want to do a regular colonoscopy instead of a virtual colonoscopy. The reason is that virtual colonoscopy does not allow the doctor to remove tissue samples or polyps.

Other times, a virtual colonoscopy is done if your doctor was not able to move the flexible tube all the way through the colon during a regular colonoscopy due to other medical reasons.

Screening for colon and rectal cancer

Your doctor will recommend screening for colon and rectal cancer at age 50 if you don’t have health problems or other factors that make you more likely to develop colon cancer ¹.

Factors that make you more likely to develop colorectal cancer include:

• someone in your family has had polyps or cancer of the colon or rectum
• a personal history of inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease
• other factors, such as if you weigh too much or smoke cigarettes

If you are more likely to develop colorectal cancer, your doctor may recommend screening at a younger age, and you may need to be tested more often.

If you are older than age 75, talk with your doctor about whether you should be screened. For more information, read the current colorectal cancer screening guidelines from the U.S. Preventive Services Task Force (https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryDraft/colorectal-cancer-screening3).

Government health insurance plans, such as Medicare, and private health insurance plans sometimes change whether and how often they pay for cancer screening tests. Check with your insurance plan to find out if and how often your insurance will cover a screening virtual colonoscopy.

Virtual colonoscopy vs Regular colonoscopy

Virtual colonoscopy is different from regular colonoscopy in several ways. Regular colonoscopy uses a long, flexible, narrow tube with a light and tiny camera on one end, called a colonoscope or scope, that is inserted into the rectum to look inside your rectum and colon (large intestine).

Virtual colonoscopy is an x-ray test that is done in the radiology department of a hospital or medical center. Unlike colonoscopy, virtual colonoscopy does not require sedation or anesthesia and no colonoscope is used.

Virtual colonoscopy takes less time.

However, virtual colonoscopy may not be as effective as colonoscopy at finding certain polyps. Also, doctors cannot remove polyps or treat certain other problems during virtual colonoscopy, as they can during colonoscopy. Your health insurance coverage for virtual colonoscopy and colonoscopy also may be different.

Virtual colonoscopy prep

To prepare for a virtual colonoscopy, you will need to talk with your doctor, change your diet, clean out your bowel, and drink a special liquid called contrast medium. The contrast medium makes your rectum and colon easier to see in the x-rays.

Talk with your doctor

You should talk with your doctor about any medical conditions you have and all prescribed and over-the-counter medicines, vitamins, and supplements you take, including:

• arthritis medicines
• aspirin or medicines that contain aspirin
• blood thinners
• diabetes medicines
• nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen
• vitamins that contain iron or iron supplements

X-rays may interfere with personal medical devices. Tell your doctor if you have any implanted medical devices, such as a pacemaker.

Doctors don’t recommend x-rays for pregnant women because x-rays may harm the fetus. Tell your doctor if you are, or may be, pregnant. Your doctor may suggest a different procedure, such as a colonoscopy.

Change your diet and clean out your bowel

As in colonoscopy, a health care professional will give you written bowel prep instructions to follow at home before the procedure. A health care professional orders a bowel prep so that little or no stool is present in your intestine. A complete bowel prep lets you pass stool that is clear and liquid. Stool inside your colon can prevent the x-ray machine from taking clear images of the lining of your intestine.

You may need to follow a clear liquid diet the day before the procedure. The instructions will provide specific direction about when to start and stop the clear liquid diet. In most cases, you may drink or eat the following:

• fat-free bouillon or broth
• gelatin in flavors such as lemon, lime, or orange
• plain coffee or tea, without cream or milk
• sports drinks in such flavors as lemon, lime, or orange
• strained fruit juice, such as apple or white grape—doctors recommend avoiding orange juice and red or purple beverages
• water

Your doctor will tell you how long before the procedure you should have nothing by mouth.

A health care professional will ask you to follow the directions for a bowel prep before the procedure. The bowel prep will cause diarrhea, so you should stay close to a bathroom.

Different bowel preps may contain different combinations of laxatives—pills that you swallow or powders that you dissolve in water and other clear liquids, and enemas. Some people will need to drink a large amount, often a gallon, of liquid laxative over a scheduled amount of time—most often the night before the procedure.

You may find this part of the bowel prep difficult; however, completing the prep is very important. The images will not be clear if the prep is incomplete.

Drink contrast medium

The night before the procedure, you will drink a contrast medium. Contrast medium is visible on x-rays and can help your doctor tell the difference between stool and polyps.

Virtual colonoscopy procedure

A specially trained x-ray technician performs a virtual colonoscopy at an outpatient center or a hospital. You do not need anesthesia.

The CT colonography exam is done as follows:

• You lie on your left side on a narrow table that is connected to an MRI or CT machine.
• Your knees are drawn up toward your chest.
• A small, flexible tube is inserted into the rectum. Air is pumped through the tube to make the colon bigger and easier to see.
• You then lie on your back.
• The table slides into a large tunnel in the CT or MRI machine. X-rays of your colon are taken.
• X-rays are also taken while you lie on your stomach.
• You must stay very still during this procedure, since movement can blur the x-rays. You may be asked to hold your breath briefly while each x-ray is taken.

A computer combines all the images to form three-dimensional pictures of the colon. The doctor can then view the images on a video monitor.

For the procedure, you will lie on a table while the technician inserts a thin tube through your anus and into your rectum. The tube inflates your large intestine with air for a better view. The table slides into a tunnel-shaped device where the technician takes the x-ray images. The technician may ask you to hold your breath several times during the procedure to steady the images. The technician will ask you to turn over on your side or stomach so he or she can take different images of the large intestine. The virtual colonoscopy procedure lasts about 10 to 15 minutes.

After a virtual colonoscopy

After a virtual colonoscopy, you can expect to:

• feel cramping or bloating during the first hour after the test
• resume your regular activities right after the test
• return to a normal diet

After the test, a radiologist looks at the images to find any problems and sends a report to your doctor. If the radiologist finds problems, your doctor may perform a colonoscopy the same day or at a later time.

Virtual colonoscopy results

Normal virtual colonoscopy findings are images of a healthy intestinal tract.

Abnormal virtual colonoscopy test results may mean any of the following:

• Colorectal cancer
• Abnormal pouches on the lining of the intestines, called diverticulosis
• Colitis (a swollen and inflamed intestine) due to Crohn disease, ulcerative colitis, infection, or lack of blood flow
• Lower gastrointestinal (GI) bleeding
• Polyps
• Tumor

Regular colonoscopy may be done (on a different day) after a virtual colonoscopy if:

• No cause for bleeding or other symptoms were found. virtual colonoscopy can miss some smaller problems in the colon.
• Problems that need a biopsy were seen on a virtual colonoscopy.

Virtual colonoscopy risks

Risks of virtual colonoscopy include:

• Exposure to radiation from the CT scan
• Nausea, vomiting, bloating, or rectal irritation from medicines used to prepare for the test
• Perforation of the intestine when the tube to pump air inserted

Inflating the colon with air has a small risk of perforating the lining of the large intestine. The doctor may need to treat perforation with surgery.

Seek care right away

If you have any of the following symptoms after a virtual colonoscopy, you should seek medical attention right away:

• severe pain in your abdomen
• fever
• bloody bowel movements or bleeding from your anus
• dizziness
• weakness

1. Final Update Summary: Colorectal Cancer: Screening. U.S. Preventive Services Task Force website. https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/colorectal-cancer-screening2[↩]