(Computed Tomography Colonography; Virtual Colonoscopy)
by Daus Mahnke, MD
CT colonography is a radiology test that looks at your large intestines, also called your colon. It is one of many options for colon cancer screenings.
Reasons for Test TOP
This test is used to look for polyps or cancers of the colon.
Possible Complications TOP
CT colonography is safe. It can be used if you are too sick to have other forms of colon cancer screening.
In some cases, a contrast material is used. One complication may be an allergic reaction to the contrast.
What to Expect TOP
Prior to Test
Description of the Test
You will be positioned on your back on a movable x-ray table. Just before the test, a small tube will be inserted into your rectum. Air will be gently pumped through this tube. The table will move slowly though the donut-shaped CT scanner. While this is happening, you will need to lie very still. You will be asked to hold your breath during the scan. The scanning test will then be repeated with you lying on your stomach.
After Test TOP
You will be able to leave after the test is done. You can resume your normal diet and activities.
How Long Will It Take? TOP
Will It Hurt? TOP
You may feel cramping and bloating. You may feel the urge to have a bowel movement.
Call Your Doctor TOP
If you were given contrast, call your doctor if you notice:
In case of an emergency, call for emergency medical services right away.
American College of Gastroenterology
National Digestive Diseases Information Clearinghouse
Canadian Association of Gastroenterology
Canadian Cancer Society
CT colonography. RadiologyInfo.org—American College of Radiology website. Available at:
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Updated May 16, 2014. Accessed September 17, 2014.
Fletcher RH. Colorectal cancer screening on stronger footing. NEJM. 2008;359:1285-1287.
Johnson CD, et al. Accuracy of CT Colonography for Detection of Large Adenomas and Cancers. NEJM. 2008;359(12): 1207-1217.
Mulhall P, Veerappan GR, Jackson JL, et al. Meta-analysis: computed tomographic colonography. Ann Intern Med. 2005;142(8):635-650.
Yee J. Screening CT Colonography. Radiol Clin North Am. 2004;42(4):757-766.
Last reviewed August 2014 by Daus Mahnke, MD
Last Updated: 9/17/2014