(Computed Tomography Colonography; Virtual Colonoscopy)
CT colonography is a radiology test that looks at the colon (large intestine). It is one of many options for colon cancer screening.
Reasons for Test
This test is used to look for polyps or cancers of the colon.
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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
Prior to Test
- Do not eat for 8-12 hours prior to the test.
- A bowel cleansing will be done with a laxative. The goal of the cleansing is to rid your colon of all stool. The laxative will cause you to have many bowel movements over several hours.
- If you have diabetes, talk to your doctor about adjusting your medications.
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.
You will be able to leave after the test is done. You can resume your normal diet and activities.
How Long Will It Take?
Will It Hurt?
You may feel cramping and bloating. You may feel the urge to have a bowel movement.
An specialist will review the images. If something abnormal is seen, your doctor may suggest a colonoscopy.
Call Your Doctor
It is important to monitor your recovery. Alert your doctor to any problems. If any of the following occur, call your doctor:
- Difficulty breathing
If you think you have an emergency, call for emergency medical services right away.
American College of Gastroenterology
National Institute of Diabetes and Digestive and Kidney Diseases
Canadian Association of Gastroenterology
Canadian Cancer Society
CT colonography. Radiology Info—American College of Radiology website. Available at: https://www.radiologyinfo.org/en/info.cfm?pg=ct_colo. Updated March 17, 2016. Accessed October 3, 2017.
Fletcher RH. Colorectal cancer screening on stronger footing. NEJM. 2008;359(12):1285-1287.
Johnson CD, Chen MH, Toledano AY, 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. 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 September 2018 by EBSCO Medical Review Board Daus Mahnke, MD Last Updated: 9/17/2014