Virtual colonoscopy compares to standard in NEJM study: Which to choose?

Colon polyp (from CDC/ Atlanta Gastroenterology Associates; Dr. Steven J. Morris)

by James Hubbard, M.D., M.P.H.

The New England Journal of Medicine published a study last week that found virtual colonoscopy is almost as accurate as the standard one in detecting polyps that can lead to colorectal cancer.

A virtual colonoscopy, called a computerized tomographic (CT) colonography in medicalese, is a fancy CAT scan that uses X-rays to look for polyps in your colon.  A regular colonoscopy (the gold standard of colorectal cancer screening) requires a long tube, with a camera on the end, inserted in the rectum, and snaked through your entire colon to look directly for abnormalities.  You remember Katie Couric’s live colonoscopy on Today, don’t you? (See video below.)

A polyp is a small stalk, usually less than 1/2 inch in diameter, growing from the lining of your intestine, that can progress to a cancerous polyp (usually takes five to 10 years for the progression).  Removing the polyps can prevent as many as 75 percent of colorectal cancers, according to the National Cancer Institute.

The problem is that people are not getting their screening colonoscopies.  What good is a test you if don’t get it? Physicians have been trying to find an alternative.  Will the virtual colonoscopy be it?


A screening colonoscopy can save a life.  Just ask someone with colon cancer if he or she thinks it’s worth the trouble.  If you have no symptoms (rectal bleeding, abdominal pain, weight loss, etc.) and no family history of colon cancer, the U.S. Preventive Services Task Force recommends getting a colonoscopy every five to 10 years after age 50. It is suggested that 50 to 60 percent don’t get the test.  Why?  Inconvenience, money, time away from work, fear.


  • It costs less.
  • It’s not invasive (except a small, enema-size tube is inserted in the rectum to pump in some carbon dioxide to expand the colon for better viewing).
  • It has minimal, if any, serious complications (the standard test can have 1 to 2 percent) and there is no sedation.

But it is not perfect.


  • It missed 10 percent of the larger polyps and more of the smaller ones.
  • If it shows a suspected polyp, you will have to have the standard colonoscopy anyway to remove it.  Seventeen percent were affected in the NEJM study.
  • You still have to have the pretest laxatives to clean out your colon.
  • There is radiation exposure.  Thought to be acceptable, with about half as much as a regular CAT scan, it still is accumulative when having one every five years or so.

So why even consider the new kind?  It is much, much, way better than having no test at all.

It will be a few years before this new test becomes mainstream.  There will be more studies and critiques.  Radiologists will need to become proficient in reading results.  As for me, I am going to stick to the gold standard. When the time comes for yours, you may have a choice.  If you are due for a test, don’t wait.  Get it now.

What are your thoughts?  Has anyone had the privilege?  Care to discuss?

Here’s a video that takes a look back at Katie Couric’s colonoscopy experience.

Picture of colon polyp courtesy CDC/Atlanta Gastroenterology Associates; Dr. Steven J. Morris.

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