Virtual Colonoscopy

This Test Is Useful In Certain Situations, Won't Replace Traditional Colonoscopy

Your doctor needs a good look at your clean colon in order to evaluate you for cancer or another condition. Image © Sebastian Kaulitzki/Science Photo Library/Getty Images

What Is A Virtual Colonoscopy?

A virtual colonoscopy is a special type of CAT scan which can evaluate the colon. The resultant three-dimensional view of the inside of the colon is valuated by a radiologist. The pictures obtained through a virtual colonoscopy are similar to a regular or optical colonoscopy, but lack color and fine detail. A virtual colonoscopy has the advantages of being quicker and less invasive than a conventional colonoscopy.

However, a virtual colonoscopy still requires that the colon be cleaned prior to the test, and is still somewhat invasive because air must be pumped into the colon. In addition, a virtual colonoscopy can miss small lesions and requires follow-up with a regular colonoscopy if polyps are found or if biopsies are needed. Finally, a virtual colonoscopy will not show flat lesions or evidence of inflammation.

This test might only be done for certain special situations because a colonoscopy is still preferred, especially for colon cancer screening. While there is still a preparation to clear the colon of stool, this differs from a colonoscopy in that the special tool used for a colonoscopy is not inserted into the body. Some people might find this test uncomfortable but it should not be painful.

Why This Test Is Used

A virtual colonoscopy can be used to screen for colon or rectal cancer if a regular colonoscopy can not be done.

As a test used to screen for colon cancer, The American Cancer Society recommends that a virtual colonoscopy be done once every 5 years for people who are over the age of 50 years. People at high risk for colon cancer because of family history or polyps may begin testing earlier, as determined by a physician.

In the case of a strong family history, a regular colonoscopy is the preferred test.

The Preparation

In order for the radiologist to have good images to work with, the colon must be empty of stool. Your gastroenterologist will give you specific instructions on how to use laxatives and enemas before the procedure to cleanse the colon. It may also be necessary to follow a liquid diet for 1 or 2 days before the procedure, and fast after midnight the night before the test.

How the Test Is Done

You will be asked to lie on your side on a table. A tube will be inserted a few inches into your rectum and a small amount of air will be pumped into your colon. This has the effect of smoothing out the inside of colon, such as when air is blown into a balloon. You will then lie still for a few minutes while a series of x-rays are taken of your abdomen. You may be asked to turn over on your side or on your back while some x-rays are taken. After the test is complete, the tube will be removed from your rectum.

After the air is introduced into the colon, you may feel fullness as if you have gas. Rarely may this cause some discomfort.


This test is generally considered to be safe and painless. There is a very small possibility that air inserted into the colon may cause injury or perforation.

However, physicians are trained to recognize and treat this problem right away. Because this test uses x-rays, it is not recommended for use in women who are or who may be pregnant.


Call your doctor in a few days for the results. If there are any findings, additional tests may be recommended. If polyps are found, a conventional colonoscopy will be needed in order to remove them.

When To Call Your Doctor

Call your doctor if you experience any abdominal pain after the test.


Jani SS. "Virtual Colonoscopy: Are We There Yet?" BenchMarks 22 Mar 2004. 15 Sept 2013.

National Institute of Diabetes and Digestive and Kidney Diseases. "Virtual Colonoscopy." National Digestive Diseases Information Clearinghouse 27 Jan 2013 2008. 15 Sept 2013.