• CT Colonography

    (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.
    Colon Polyps
    Nucleus Image
    Copyright © Nucleus Medical Media, Inc.

    Possible Complications

    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.

    After Test

    You will be able to leave after the test is done. You can resume your normal diet and activities.

    How Long Will It Take?

    30-40 minutes

    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:
    • Nausea
    • Itching
    • Difficulty breathing
    If you think you have an emergency, call for emergency medical services right away.


    American College of Gastroenterology http://gi.org

    National Institute of Diabetes and Digestive and Kidney Diseases https://www.niddk.nih.gov


    Canadian Association of Gastroenterology https://www.cag-acg.org

    Canadian Cancer Society http://www.cancer.ca


    CT colonography. Radiology Info—American College of Radiology website. Available at: https://www.radiologyinfo.org/en/info.cfm?pg=ct%5Fcolo. 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.

    Revision Information

    • Reviewer: EBSCO Medical Review Board Daus Mahnke, MD
    • Update Date: 09/17/2014
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