CT Colonography
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CT Colonography

(Computed Tomography Colonography; Virtual Colonoscopy)


CT colonography is a radiology test that allows doctors to look for polyps or cancers of the colon. It is one of many options that can be used for colon cancer screening. The other options for colon cancer screening are:

Colon Polyps

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Each of the above options has advantages and disadvantages. The main advantage to CT colonography is that it is very safe and can be used in people who are too sick to undergo other forms of colon cancer screening (such as flexible sigmoidoscopy or colonoscopy). It may also be available in locations where the other screening tools are not available. The main disadvantage is that it may not be covered by medical insurance. Also, at the present time, medical experts disagree about the effectiveness of CT colonography as a colon cancer screening tool. But, as more doctors learn how to do this test, it will become more common and more trusted.

Be sure to discuss the various colon cancer screening options with your physician. Currently most medical groups suggest “traditional” fiber optic colonoscopy as the screening method of choice, if it is available.

Parts of the Body Involved

  • Colon
  • Rectum

Reasons for Procedure

CT colonography is one option you have for colon cancer screening. Be sure you discuss all your options for colon cancer screening with your doctor before choosing to have CT colonography.

Risk Factors for Complications During the Procedure


What to Expect

Prior to Procedure

  • You cannot eat for 8-12 hours before the procedure.
  • You will undergo a bowel cleansing with a laxative (similar to what is needed before colonoscopy). The goal of this laxative 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 , discuss your medications with your doctor.



Description of the Procedure

A radiologist will position you on your back on a movable x-ray table. Just before the procedure, a small tube will be inserted into your rectum. Air will then be gently pumped into your colon through this tube. The table will move slowly though the donut-shaped CT scanner. While this is happening, it is important that you lay very still. You will be asked to hold your breath during the scan. The scanning procedure will then be repeated with you lying on your stomach.

After Procedure

No post procedure recovery time is necessary. You will be allowed to leave right after the procedure.

How Long Will It Take?

The test will take 30-40 minutes.

Will It Hurt?

You may feel cramping, bloating, or the need to have a bowel movement.

Possible Complications

If used, some people can have an allergic reaction to IV contrast dye.

Average Hospital Stay

None. The procedure is done on an outpatient basis.

Postoperative Care

  • Resume your normal diet, unless told otherwise by your doctor.
  • Resume your medications, unless told otherwise by your doctor.


If something abnormal is seen using CT colonography, your doctor may recommend you undergo colonoscopy. Colonoscopy is necessary after CT colonography 30%-50% of the time.

Call Your Doctor If Any of the Following Occurs

If you were given contrast, contact your healthcare provider if you notice:

  • Nausea
  • Itching
  • Difficulty breathing


American College of Gastroenterology (ACG)

National Digestive Diseases Information Clearinghouse


Canadian Association of Gastroenterology

Canadian Cancer Society


Fletcher RH. Colorectal Cancer Screening on Stronger Footing. NEJM 2008:359(12): 1285-1287.

Gore RM, Levine MS. Textbook of Gastrointestinal Radiology . 2nd ed. Philadelphia: WB Saunders Company; 2000.

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 September 2008 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.

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