Virtual colonoscopy (VC) is an imaging or x-ray test that looks for cancer, polyps, or other disease in the large intestine (colon).
Virtual colonoscopy is different from a regular colonoscopy. Regular colonoscopy uses a long, lighted tool called a colonoscope that is inserted into the rectum and large intestine.
Virtual colonoscopy is done in the radiology department of a hospital or medical center. No sedatives are needed and no colonoscope is used.
The exam is done as follows:
A computer combines all the images to form three-dimensional pictures of the colon. The doctor can then view the images on a video monitor.
Your bowels need to be completely empty for the exam. A problem in your large intestine that needs to be treated may be missed if your intestines are not cleaned out.
Your health care provider will give you the steps for cleansing your bowels. This is called bowel preparation. Steps may include using enemas, not eating solid foods for 2 or 3 days before the test, and taking laxatives.
You need to drink plenty of clear liquids for 1 to 3 days before the test. Examples of clear liquids are:
You will likely be told to stop taking aspirin, ibuprofen, naproxen, or other blood-thinning medicines for several days before the test. Keep taking your other medicines unless your doctor tells you otherwise.
You will need to stop taking iron pills or liquids a few days before the test, unless your health care provider tells you it is okay to continue. Iron can make your stool dark black. This makes it harder for the doctor to view inside your bowel.
CT and MRI scanners are very sensitive to metals. Do not wear jewelry the day of your exam. You will be asked to wear a hospital gown for the procedure.
The x-rays are painless. Pumping air into the colon can create cramping or gas pains.
Virtual colonoscopy may done for the following reasons:
Your doctor may want to do a regular colonoscopy instead of a virtual colonoscopy. The reason is that virtual colonoscopy does not allow the doctor to remove tissue samples or polyps.
Other times, a virtual colonoscopy is done if your doctor was not able to move the flexible tube all the way through the colon during a regular colonoscopy.
Normal findings are images of a healthy intestinal tract.
Regular colonoscopy may be done (on a different day) after a virtual colonoscopy if:
Risks of virtual colonoscopy include:
Differences between virtual and conventional colonoscopy include:
Colonoscopy - virtual; CT colonography; Computed tomographic colonography; Colography - virtual
Itzkowitz SH, Potack J. Colonic polyps and polyposis syndromes. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease Pathophysiology/Diagnosis/Management. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2010:chap 122.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines): Colorectal cancer screening. Version 2.2013. Available at: www.nccn.org/professionals/physician_gls/pdf/colorectal_screening.pdf. Accessed October 2013.
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Updated by: George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
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