Colonoscopy is the inspection of the entire large intestine (colon) using a long, flexible, lighted viewing scope (colonoscope), which is usually linked to a video monitor similar to a TV screen. A colonoscopy may be done to screen for cancer or to investigate symptoms, such as bleeding.

Colonoscopy is done in the hospital or a doctor's office that has the necessary equipment. Preparation for the test includes emptying the bowels ahead of time using a laxative or enema. The person undergoing colonoscopy is given medicine to relieve pain and to make him or her drowsy. The test usually takes 30 to 45 minutes, but it may take longer, depending upon what is found and what is done during the test.

A doctor will collect a tissue sample (biopsy) from any abnormal area. The tissue is then analyzed by a pathologist.