Virtual colonoscopy, also called CT colonography, is a relatively new test that is not generally covered by insurance. The test creates images of the inside of the colon by taking a CT scan from outside of the body. It is a screening only, so if it shows any polyps (pre-cancerous growths), it needs to be followed up with a colonoscopy to remove them.
Your bowel needs to be as clean and empty as possible for the CT images to show polyps clearly. Your prep will depend on your doctor's preference, but is typically similar to either a colonoscopy or sigmoidoscopy. There are often dietary and medication restrictions in the days prior to the test.
The test is conducted in a room with a CT scanner in a medical facility. When you are ready, a small amount of air is inserted into your bowel. This might be slightly uncomfortable. You will lie still on a bed for about 10 minutes as the scanner moves over your body taking x-rays. The entire procedure takes 30-60 minutes. Sedation is not used.
When the imaging is finished, you may dress on your own, drive home, and resume your normal diet and activities (unless your physician tells you otherwise). The x-rays will be constructed into 3D images of your colon. A specialist will scan the images for polyps.
You should hear results within a week or two of your procedure, at which point you should discuss a follow-up plan with your primary doctor. If a virtual colonoscopy detects an abnormal growth, you will need to have a colonoscopy to remove it. Abnormal growths are detected in about 1 out of 5 people. It’s possible the CT scan will reveal something outside of the colon which could require additional testing. While sometimes these findings save lives, they can also cause unnecessary worry.
Everyone should continue colon screening regularly between the ages of 50 and 75. The timing has not been studied closely, but some doctors suggest that a virtual colonoscopy be repeated every 5 years if no polyps are found and you have no other risk factors. Talk to your doctor about the specifics of your screening plan past the age of 75.
- Possible Harms
- Less invasive way to look for polyps
- Relatively quick
- Few complications
- No sedation
- May unexpectedly reveal treatable problems outside of the colon
- Moderate to full bowel prep
- Slight discomfort when air is put into bowel
- May miss smaller polyps or cancers
- Cannot remove or biopsy polyps
- May reveal abnormalities outside of the colon that cause unnecessary testing and concern
- Poor insurance coverage
- Radiation exposure
- If polyps are found, regular colonoscopy must be done to remove them, which may require a second session of bowel prep
- Radiation exposure may slightly increase risk of cancer
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