Health Topics for Tests and Exams

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Cellular Immunology Diagnostic Lab

Colonoscopy

Colonoscopy is a visual examination of the lining of the large intestine. It uses a tool called a fiberoptic endoscope. An endoscope is a long, thin, flexible tube that can be passed through the entire length of the large intestine. The fibers of the endoscope transmit light and a video image. The examiner can also pass surgical tools through the endoscope.

Colonoscopy is used to evaluate the following conditions:

• blood in the stool or unexplained rectal bleeding

• intestinal narrowing or blockage

• inflammation or ulcerative disease and

• screening for polyps and cancer

The large intestine must be thoroughly clean to be clearly visible. The person goes on a liquid diet for 48 hours before the test, uses a laxative the night before, and, on the morning of the test, takes an enema. The test can be done as an outpatient procedure. It usually lasts 30 to 60 minutes. A mild sedative is often given to help relax the person.

At the start of the test the person lies on his side. The endoscope is well lubricated for easy insertion through the rectum. The person may feel the urge to defecate, but it is rarely painful. The examiner often pumps air into the intestine to get a better view. It is normal for this air to escape as flatulence during the test and for a while after the test.

The examiner can view the entire lining on a TV monitor. Images can be transferred to photographs and kept for comparison with future tests. The examiner can take biopsies or remove polyps.

Polyps are small outgrowths from the lining of the intestine. They commonly occur as people age. Although they are not cancer, they have the potential to become cancer. If the examiner removes any polyps, the person may briefly have blood in the stool. A repeat colonoscopy is recommended in 3 years to look for missed or new polyps. If none are found in follow-up, repeat tests are recommended every 5 years.

The American Cancer Society recommends a limited colonoscopy every 3 to 5 years for all persons after age 50.

Consult the UI Health Care Cancer Information Service for more information about this topic.

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