Virtual colonoscopy (VC) uses x rays and

computers to produce two- and threedimensional images of the colon (large

intestine) from the lowest part, the rectum,

all the way to the lower end of the small

intestine and display them on a screen.

The procedure is used to diagnose colon

and bowel disease, including polyps, diverticulosis, and cancer. VC can be performed

with computed tomography (CT), sometimes called a CAT scan, or with magnetic

resonance imaging (MRI).

VC Procedure

While preparations for VC vary, you will

usually be asked to take laxatives or other

oral agents at home the day before the procedure to clear stool from your colon. You

may also be asked to use a suppository to

cleanse your rectum of any remaining fecal

matter.

VC takes place in the radiology department

of a hospital or medical center. The examination takes about 10 minutes and does not

require sedatives. During the procedure, 

• The doctor will ask you to lie on your

back on a table.

• A thin tube will be inserted into your

rectum, and air will be pumped

through the tube to inflate the colon

for better viewing. 

• The table moves through the scanner

to produce a series of two-dimensional

cross-sections along the length of the

colon. A computer program puts

these images together to create a

three-dimensional picture that can

be viewed on the video screen.

• You will be asked to hold your breath

during the scan to avoid distortion on

the images.

• The scanning procedure is then

repeated with you lying on your

stomach.

After the examination, the information

from the scanner must be processed to

create the computer picture or image of

your colon. A radiologist evaluates the

results to identify any abnormalities.

You may resume normal activity after the

procedure, although your doctor may

National Digestive Diseases Information Clearinghouse

National

Institute of

Diabetes and

Digestive 

and Kidney

Diseases

NATIONAL 

INSTITUTES

OF HEALTH

Virtual

Colonoscopy

U.S. Department

of Health and

Human Services

Conventional Colonoscopy

In a conventional colonoscopy, the

doctor inserts a colonoscope—a long,

flexible, lighted tube—into the patient’s

rectum and slowly guides it up through

the colon. Pain medication and a mild

sedative help the patient stay relaxed

and comfortable during the 30- to 60-

minute procedure. A tiny camera in

the scope transmits an image of the

lining of the colon, so the doctor can

examine it on a video monitor. If an

abnormality is detected, the doctor can

remove it or take tissue samples using

tiny instruments passed through the

scope.

For more information about conventional colonoscopy, please see the

Colonoscopy fact sheet from the National Institute of Diabetes and Digestive

and Kidney Diseases (NIDDK).
ask you to wait while the test results are

analyzed. If abnormalities are found and

you need conventional colonoscopy, it may

be performed the same day.

Advantages of VC

VC is more comfortable than conventional

colonoscopy for some people because it

does not use a colonoscope. As a result, no

sedation is needed, and you can return to

your usual activities or go home after the

procedure without the aid of another person. VC provides clearer, more detailed

images than a conventional x ray using a

barium enema, sometimes called a lower

gastrointestinal (GI) series. It also takes

less time than either a conventional

colonoscopy or a lower GI series.

Disadvantages of VC

The doctor cannot take tissue samples or

remove polyps during VC, so a conventional colonoscopy must be performed if

abnormalities are found. Also, VC does

not show as much detail as a conventional

colonoscopy, so polyps smaller than 10 millimeters in diameter may not show up on

the images.

For More Information 

American College of Gastroenterology

(ACG)

4900–B South 31st Street

Arlington, VA 22206–1656

Phone: 703–820–7400

Fax: 703–931–4520

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

Fax: 414–964–7176

Email: iffgd@iffgd.org

Internet: www.iffgd.org

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES

National Institutes of Health

NIH Publication No. 03–5095

May 2003

National Digestive Diseases

Information Clearinghouse

2 Information Way

Bethesda, MD 20892–3570

Phone: 1–800–891–5389

Fax: 703–738–4929

Email: nddic@info.niddk.nih.gov

Internet: www.digestive.niddk.nih.gov

The National Digestive Diseases Information

Clearinghouse (NDDIC) is a service of the

National Institute of Diabetes and Digestive

and Kidney Diseases (NIDDK). The NIDDK

is part of the National Institutes of Health

under the U.S. Department of Health and

Human Services. Established in 1980, the

clearinghouse provides information about

digestive diseases to people with digestive

disorders and to their families, health care

professionals, and the public. NDDIC answers

inquiries, develops and distributes publications,

and works closely with professional and patient

organizations and Government agencies to

coordinate resources about digestive diseases.

Publications produced by the clearinghouse are

carefully reviewed by both NIDDK scientists

and outside experts. This fact sheet was

reviewed by Douglas K. Rex, M.D., Indiana

University School of Medicine.

This publication is not copyrighted. The

clearinghouse encourages users of this fact

sheet to duplicate and distribute as many

copies as desired.

This fact sheet is also available at 

www.digestive.niddk.nih.gov.