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Verdict Still Out on Virtual Colonoscopy

< Sep. 14, 2011 > -- Although virtual colonoscopy has been heralded as the next best screening test for colorectal cancer, not all experts are on board.

Photo of doctor and patient

And half of the patients who might benefit from the screening are avoiding it, as well as the standard colonoscopy, the CDC says. That may be because both the virtual colonoscopy - a noninvasive alternative - and the standard test require a daunting amount of unpleasant preparation.

Experts who argue in favor of the virtual test say the technology behind it has advanced enough that the American Cancer Society recommends it and the American College of Gastroenterology (ACG) says it's a viable alternative to the "gold standard" colonoscopy.

Different view

A virtual colonoscopy offers a view of the colon via CT or MRI imaging and requires no sedation. In a standard colonoscopy, the doctor inserts a long, lighted, flexible tube called a colonoscope into the colon, or large intestine. Patients undergoing a standard colonoscopy must be sedated before the colonoscope is used.

In both versions of the screening test, the doctor is looking for polyps, or precancerous growths.

Because a patient who has a virtual colonoscopy doesn't need to be sedated, he or she can return to daily activities immediately. A person who is sedated isn't allowed to drive for several hours afterward.

Test limitations

But other experts say the virtual colonoscopy has several critical drawbacks: Polyps found during imaging still need to be removed - so a patient with a polyp would still need a standard colonoscopy to confirm that the polyp was there and remove it.

And virtual colonoscopy can't always detect polyps smaller than 5 millimeters, but that size of polyp, or even smaller, makes up about 80 percent of polyps found, the ACG says.

False positives

The test also produces a considerable number of false positives, suggesting a problem that turns out to not be there. But, determining that requires people to undergo a normal colonoscopy.

"They not only are not detecting a sizable number of polyps, they are calling polyps that aren't there," says David A. Johnson, M.D., co-author of the ACG's guidelines for colorectal cancer screening.

And yet another drawback, opponents say, is that the virtual colonoscopy exposes patients to radiation, but a standard colonoscopy does not.

The ACG says, however, that a virtual colonoscopy is an option for people who refuse to get a standard colonoscopy. A virtual colonoscopy should be done every five years.

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Colorectal Cancer Screening Guidelines

The American Cancer Society recommends that both men and women should begin screening tests for colorectal cancer at age 50. Talk with your health care provider about which test is appropriate for you:

  • Annual fecal occult blood test (FOBT) or fecal immunochemical test (FIT) and flexible sigmoidoscopy (FSIG) every five years

  • FOBT or FIT every year

  • FSIG every five years

  • Double-contrast barium enema every five years

  • Colonoscopy every 10 years

If you have any of the following risk factors, you may need to begin screening at an earlier age or have more frequent screening:

  • Strong family history of colorectal cancer or adenomatous polyps in a parent or sibling before age 60, or in two first-degree relatives of any age

  • Family history of hereditary colorectal cancer syndromes, such as familial adenomatous polyposis or hereditary nonpolyposis colon cancer

  • Personal history of colorectal cancer or adenomatous polyps

  • Personal history of chronic inflammatory bowel disease

Always talk with your health care provider to find out more information.

Online Resources

(Our Organization is not responsible for the content of Internet sites.)

American College of Gastroenterology - What Questions Should You Ask?

National Cancer Institute - Colorectal Cancer Screening

National Institute of Diabetes and Digestive and Kidney Diseases - Virtual Colonoscopy