Virtual Colonoscopy (CT Colonography)

Author: Courtney Misher, MPH, BS R.T.(T)
Last Reviewed: August 01, 2022

A virtual colonoscopy is a test that uses a CT scan to take pictures of your colon and rectum. This is done from outside of your body and you do not need general anesthesia. It is used to find ulcers, polyps, and cancer. It can be used as a screening exam for colon cancer in people aged 45 or older. It can also be called CT colonography.

How do I prepare for a virtual colonoscopy?

Your provider will give you specific instructions to prepare for the test. Often you will need to:

  • Be on a clear liquid diet for 1 to 2 days before the test.
  • Empty your colon by taking a laxative the night before the test.
  • Drink contrast medium right before the scan to help your provider see your colon and rectum.
  • Talk to your provider about all medications you take. You may need to stop taking or change the dose of some medications before your test.

How is this test performed?

You will put on a hospital gown. You will lie on an exam table on your side with your knees pulled up towards your chest. A small tube will be placed into your rectum to fill your colon with air or carbon dioxide. You will then turn onto your back and the exam table will slide into the CT machine. Pictures will be taken while you are on your back and then again while lying on your side and/or on your stomach. You may be told to hold your breath at different times during the test. The test usually takes about 10-15 minutes.

What to expect after your virtual colonoscopy?

Unless instructed otherwise, you can return to normal activities and a normal diet after the test. You may feel bloated and may pass more gas than normal while your body gets rid of the gas that was put into your colon for the test.

How do you receive the results of your virtual colonoscopy?

Following the test, your provider will talk to you about the findings. If they see polyps or tissue that does not appear to be normal, they may recommend more testing, including a traditional colonoscopy. If all the findings were normal, then your provider will likely ask you to repeat the test in 5 years.

U.S. Department of Health and Human Services. (n.d.). Virtual colonoscopy. National Institute of Diabetes and Digestive and Kidney Diseases. Retrieved August 1, 2022, from

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