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Virtual Colonoscopy - Topic Overview

What is a virtual colonoscopy?

A virtual colonoscopy uses X-rays and computers (computed tomography [CT] or magnetic resonance imaging [MRI]) to take two- or three-dimensional images of the interior lining of your large intestine camera.gif (colon) and rectum. A virtual colonoscopy can be used to screen for precancerous and cancerous growths in the colon or rectum (colorectal cancer), such as polyps or tumors.

Virtual colonoscopy (also called computed tomographic colonography, or CTC) is still being studied to determine whether the results are as accurate as a regular colonoscopy. Virtual colonoscopy is not yet widely available.

Virtual colonoscopy is one of many tests that may be used to screen for colon cancer. Which screening test you choose depends on your risk, your preference, and your doctor. Talk to your doctor about what puts you at risk and what test is best for you.

For more information on screening tests for colon cancer, see:

Colon Cancer: Which Screening Test Should I Have?

Why is it done?

A virtual colonoscopy may be done to:

  • Screen for colorectal cancer or polyps.
  • Monitor the growth of polyps.
  • Screen for recurrence of colorectal cancer in people who have had surgery for this disease.
  • Evaluate abnormal results from other colon tests.
  • Replace a regular colonoscopy if the thin lighted scope cannot be inserted in the colon for some reason, such as when a tumor blocks the passage.

Virtual colonoscopy is not commonly done for other conditions at this time but may prove to be useful to:

  • Detect other problems or diseases of the anus, rectum, or large intestine (colon).
  • Check the source of internal bleeding.
  • Check the cause of chronic diarrhea.
  • Monitor the treatment of inflammatory bowel disease.

How do I prepare for it?

Virtual colonoscopy requires the same cleansing colon prep as a regular colonoscopy. Colon prep takes 1 to 2 days depending on which type of prep your doctor recommends. For many people, the prep for a colonoscopy is more trying than the actual test. Researchers are studying methods that could be used to mark (tag) stool in the colon before virtual colonoscopy so cleansing colon preps would not be needed.

Before this test, you will need to clean out your colon. The following information gives you a general idea of the preparation for a colonoscopy. Your doctor will give you specific instructions before your test.

  • One to two days before a colonoscopy, you will stop eating solid foods and drink only clear fluids, such as water, tea, coffee, clear juices, clear broths, Popsicles, and gelatin (such as Jell-O).
  • Your doctor will recommend a medicine for you to use to prepare for your colonoscopy. It will most likely be a prescription laxative tablet and/or a laxative solution (such as Nulytely or Golytely) that you drink before your colonoscopy. This solution will be given to you as a powder that you will mix with 1 gal (3.8 L) of water. You may need to drink this laxative solution over 1 to 2 hours in the evening before the test. Or you may be asked to drink half the solution the evening before your test and the other half the morning of your test. This solution may taste very salty and may make you feel sick to your stomach. To make your colon prep easier, you may want to try some of the following tips:
    • You may find it easier to drink the solution if you use a straw with the end at the back of your throat (to bypass the taste buds).
    • Each time you drink some of the solution, you may also drink some water or clear fluids (like apple juice) to help get rid of the salty taste in your mouth.
    • You may find it easier to drink the solution if you chill it in the refrigerator first.
    • Ask your doctor if it is okay for you to add flavored drink crystals (such as Crystal Light) to the solution.
    • Add lemon juice to the solution or suck on sliced lemon wedges after you take a drink.
  • Your doctor may recommend a different preparation product, such as the Nutraprep meal kit or sodium phosphate tablets (for example, Visicol). These are other methods of preparing for a colonoscopy. If you are concerned about the bowel prep, you can ask your doctor whether another method will work for you.
    • Oral sodium phosphate (either tablets or liquid) can cause kidney problems. Make sure you check with your doctor before using a nonprescription sodium phosphate product.
  • You will want to stay home while doing the colon prep because it will make you use the bathroom often.
  • Drink plenty of clear fluids during the prep so you will not get dehydrated. This will also help clean out your colon completely after you finish the colon prep.
  • Do not eat any solid foods after doing the colon prep.
  • Stop drinking clear liquids 6 to 8 hours before the test.
  • Your doctor may have you use an enema 30 to 60 minutes before the test to completely clean out your colon.
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WebMD Medical Reference from Healthwise

Last Updated: December 07, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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