Virtual Colonoscopy

National Digestive Diseases Information Clearinghouse

Virtual colonoscopy (VC) uses x rays and • You will be asked to hold your breath computers to produce two- and three- during the scan to avoid distortion on dimensional images of the colon (large the images. intestine) from the lowest part, the rectum, • The scanning procedure is then National all the way to the lower end of the small Institute of repeated with you lying on your Diabetes and intestine and display them on a screen. Digestive stomach. and Kidney The procedure is used to diagnose colon Diseases and bowel disease, including polyps, diver- After the examination, the information ticulosis, and cancer. VC can be performed from the scanner must be processed to NATIONAL INSTITUTES with computed tomography (CT), some- create the computer picture or image of OF HEALTH times called a CAT scan, or with magnetic your colon. A radiologist evaluates the resonance imaging (MRI). results to identify any abnormalities. You may resume normal activity after the VC Procedure procedure, although your doctor may While preparations for VC vary, you will usually be asked to take laxatives or other oral agents at home the day before the pro- cedure to clear stool from your colon. You Conventional Colonoscopy may also be asked to use a suppository to In a conventional colonoscopy, the cleanse your rectum of any remaining fecal doctor inserts a colonoscope—a long, matter. flexible, lighted tube—into the patient’s VC takes place in the radiology department rectum and slowly guides it up through of a hospital or medical center. The exami- the colon. Pain medication and a mild nation takes about 10 minutes and does not sedative help the patient stay relaxed require sedatives. During the procedure, and comfortable during the 30- to 60- minute procedure. A tiny camera in • The doctor will ask you to lie on your the scope transmits an image of the back on a table. lining of the colon, so the doctor can • A thin tube will be inserted into your examine it on a video monitor. If an rectum, and air will be pumped abnormality is detected, the doctor can through the tube to inflate the colon remove it or take tissue samples using for better viewing. tiny instruments passed through the scope. • The table moves through the scanner to produce a series of two-dimensional For more information about conven- cross-sections along the length of the tional colonoscopy, please see the colon. A computer program puts Colonoscopy fact sheet from the Nation- al Institute of Diabetes and Digestive U.S. Department these images together to create a of Health and three-dimensional picture that can and Kidney Diseases (NIDDK). Human Services be viewed on the video screen. ask you to wait while the test results are National Digestive Diseases analyzed. If abnormalities are found and you need conventional colonoscopy, it may Information Clearinghouse be performed the same day. 2 Information Way Bethesda, MD 20892–3570 Advantages of VC Phone: 1–800–891–5389 Fax: 703–738–4929 VC is more comfortable than conventional Email: [email protected] colonoscopy for some people because it Internet: www.digestive.niddk.nih.gov does not use a colonoscope. As a result, no The National Digestive Diseases Information sedation is needed, and you can return to Clearinghouse (NDDIC) is a service of the your usual activities or go home after the National Institute of Diabetes and Digestive procedure without the aid of another per- and Kidney Diseases (NIDDK). The NIDDK son. VC provides clearer, more detailed is part of the National Institutes of Health images than a conventional x ray using a under the U.S. Department of Health and barium enema, sometimes called a lower Human Services. Established in 1980, the gastrointestinal (GI) series. It also takes clearinghouse provides information about less time than either a conventional digestive diseases to people with digestive colonoscopy or a lower GI series. disorders and to their families, health care professionals, and the public. NDDIC answers Disadvantages of VC inquiries, develops and distributes publications, and works closely with professional and patient The doctor cannot take tissue samples or organizations and Government agencies to remove polyps during VC, so a conven- coordinate resources about digestive diseases. tional colonoscopy must be performed if abnormalities are found. Also, VC does Publications produced by the clearinghouse are not show as much detail as a conventional carefully reviewed by both NIDDK scientists colonoscopy, so polyps smaller than 10 mil- and outside experts. This fact sheet was reviewed by Douglas K. Rex, M.D., Indiana limeters in diameter may not show up on University School of Medicine. the images. For More Information This publication is not copyrighted. The American College of Gastroenterology clearinghouse encourages users of this fact (ACG) sheet to duplicate and distribute as many 4900–B South 31st Street copies as desired. Arlington, VA 22206–1656 Phone: 703–820–7400 This fact sheet is also available at Fax: 703–931–4520 www.digestive.niddk.nih.gov. Internet: www.acg.gi.org International Foundation for Functional Gastrointestinal Disorders (IFFGD) P.O. Box 170864 Milwaukee, WI 53217 Phone: 1–888–964–2001 or 414–964–1799 U.S. DEPARTMENT OF HEALTH Fax: 414–964–7176 AND HUMAN SERVICES Email: [email protected] National Institutes of Health Internet: www.iffgd.org NIH Publication No. 03–5095 May 2003