What is a CT colonography (virtual colonoscopy)?

A Answers (6)

  • A CT colonography is an advanced type of computed tomography (CT or CAT) scan of the colon and rectum. A CT scan is an x-ray test that produces detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures into images of slices of the part of your body being studied. For CT colonography, special computer programs create both two dimensional x-ray pictures and a three-dimensional "fly-through" view of the inside of the colon and rectum, which allows the doctor to look for polyps or cancer.

    This test may be especially useful for some people who can't have or don't want to have more invasive tests such as colonoscopy. It can be done fairly quickly and does not require sedation. But even though this test is not invasive like colonoscopy, it still requires the same type of bowel preparation and uses a tube placed in the rectum (similar to the tube used for barium enema) to fill the colon with air. Another possible drawback is that if polyps or other suspicious areas are seen on this test, a colonoscopy will still likely be needed to remove them or to explore them fully.
  • ADr. Daniel M. Labow, MD, Surgical Oncology, answered on behalf of The Mount Sinai Health System

    Virtual colonoscopy uses specialized CT Scan images to examine the colon, so it does exposes the patient to the radiation of a CT Scan. It can be very accurate, but it does not allow for any biopsies. If an abnormality is found, a regular colonoscopy is needed. In addition, patients must prepare for a virtual colonoscopy in the same way they prepare for a traditional colonoscopy as the colon must be completely clean so the doctor has a clear view of your intestines.   

  • ADr. Manoj Mehta, MD, Gastroenterology, answered on behalf of NorthShore University HealthSystem
    A traditional colonoscopy has the ability to not just identify polyps, but remove them, so a traditional colonoscopy and virtual colonoscopy are not really equivalent. A virtual colonoscopy is more like a barium enema or a high-tech lower GI x-ray. Because of the limitations with a virtual colonoscopy, the current consensus is that virtual colonoscopy is not ready for "prime time", however, this may be an option in the future.
  • ADr. Mehmet Oz, MD, Cardiology (Cardiovascular Disease), answered
    Virtual colonoscopy (computerized tomographic colonography) is a new type of screening method that uses a CT scanner to visualize the colon. A device is inserted at the rectum but does not ascend up past the sigmoid portion of the colon. It is less uncomfortable but a colonoscopy will still be required if a polyp is found. Bowel prep is still necessary.
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  • ADr. Grace Elta, MD, Gastroenterology, answered on behalf of American Society for Gastrointestinal Endoscopy
    CT colonography, also referred to as virtual colonoscopy, relies on a computer program to generate a 3D picture of the large intestine (colon) using x-ray images. This differs from colonoscopy, which provides actual photos of the colon and rectum via a camera attached to a thin, flexible scope that is physically guided through the large intestine.

    With virtual colonoscopy, a small tube is placed in the rectum and air is pumped into the colon to inflate the bowel. Then a special CT scan is used to image the colon. Studies show that it is effective in identifying medium to large polyps, but is ineffective in identifying small polyps. CT colonography may be best for low-risk patients who cannot undergo or who failed a conventional colonoscopy. The same bowel prep as conventional colonoscopy is required and it does not use sedation. The procedure uses X-ray radiation and if polyps or other abnormalities are found, a conventional colonoscopy must be performed. Virtual colonoscopy is not covered by Medicare or most other payers as an initial screening test.
  • CT colonography is a CT scan, or a radiology test. It's an x-ray of the colon. It can be a very useful test, but some people aren’t aware that to have this test they still need to do an entire bowel cleanse.

    There is also a small risk of perforation, which is also a risk with colonoscopy. Here’s the other caveat: If a polyp is found on your CT colonography, you have to have a colonoscopy and you have to do a bowel cleanse again. But if we're doing this test because we could not get to the end of your colon with a colonoscopy, which is rare but possible, this may be a good test.

    CT colonography was rising in popularity along with the flat polyp phenomenon. But there’s really been no evidence that’s shown whether the CT colonography is even good at detecting flat colon polyps.
Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.
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