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CT Colonography

(Computed Tomography Colonography; Virtual Colonoscopy)
  • Definition

    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.
    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 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:
    • Nausea
    • Itching
    • 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. American College of Radiology Radiology Info website. Available at: Updated May 16, 2014. Accessed September 17, 2014.

    Fletcher RH. Colorectal cancer screening on stronger footing. NEJM. 2008(12);359:1285-1287.

    Johnson CD, Chen MH, et al. Accuracy of CT colonography for detection of large adenomas and cancers. NEJM. 2008;359(12): 1207-1217.

    Mulhall P, Veerappan GR, 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.

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