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Virtual Colonoscopy or Computed Tomography Colonography is a minimally invasive diagnostic test that uses an x-ray machine to scan the patient’s abdomen and pelvis. Several hundred images are then compiled with software to show the inside of the colon in two- and three-dimension. Virtual Colonoscopy helps to detect polyps (pre-cancerous growths), and colon cancer.

The National Institutes of Health estimate that In 2009, there will be 106,100 new cases of colon cancer and 40,870 new cases of rectal cancer. What's more, 49,920 Americans will be expected to die of colon or rectal cancer.

But when detected early, 90% of adults are cured. However, over 50% of adults over 50 who should be screened for colorectal cancer don't submit to a traditional, invasive form of colonoscopy or sigmoidoscopy, an exam of the lower large bowel, because they fear pain or injury, can't afford to pay for the test, don't think they need the test, or don't know about the test.

Advantages of virtual colonoscopy

• No sedative is required.
• No scope is thread through the colon, so procedure is less invasive.
• Low risk of colon perforation or bleeding due to polyps removal. Therefore, patients on blood thinning medication can take this test.
• Increases number of patients who are willing to undergo this minimally invasive form of colon cancer screening.
• Abnormalities outside the colon are discovered in about 5 % of patients.
• More cost-effective than optical colonoscopy.
• Patient can go home shortly after the test if no abnormalities are discovered.
• Test can be done if traditional colonoscopy cannot be done or completed. Example: patient has bowel obstruction or ulcerative colitis.

• Patients must still submit to bowel emptying.
• Patients will probably have cramps when colon is filled with air.
• Smaller polyps may not be detected and false positives can occur.
• This is a strictly a diagnostic test. Polyps cannot be removed during test. Biopsies cannot be performed. Therefore, patient will need a traditional colonoscopy if polyps or other abnormalities are discovered.
• Test should not be performed if patient is pregnant.
• There is a small risk that colon inflation can perforate the colon. But this occurs in less than 1 in 2,000 patients.
• Patient is exposed to radiation.
• Test may not be covered by health insurance unless the procedure is necessary, for instance, in the case of scarring.
• If you are 50 years and older, have disease of the colon or have a family history of colon cancer, discuss your cancer screening options with your physicians.

National Institutes of Health (NIH)
What you need to know about cancer of the colon and rectum
http://www.cancer.gov/cancertopics/wyntk/colon-and-rectal

Image of colon. Credit: Therese Winslow, NIH

ast modified: 05/24/09