(Computed Tomography Colonography; Virtual Colonoscopy)
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
This test is used to look for polyps or cancers of the colon.
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.
An expert will review the images. If something abnormal is seen, your doctor may suggest a colonoscopy.
Call Your Doctor
If you were given contrast, call your doctor if you notice:
- Difficulty breathing
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: http://www.radiologyinfo.org/en/info.cfm?pg=ct_colo. 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
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.