The shorter instrument that examines the lower one third of the colon, called a flexible sigmoidoscopy, should not be used. The colon cancers are often found in the right colon and cannot be detected with the sigmoidoscope. A colonoscope is a thin, flexible tube that is passed into the colon. It has a light on the end and allows the doctor examine the lining of all 6 feet of the colon. In addition, instruments can be passed through the scope to sample or remove polyps.
Patients drink a special solution to cleanse the colon the night before the test.
The doctor usually gives a sedative through the vein just before inserting the scope. The exam of the entire 6 feet of the colon takes about 20 minutes and is usually quite comfortable. Patients cannot drive for about 8 hours after the procedure because of the effects of the sedative. Someone must drive the patient home but light duties can be resumed the rest of the day. Surgical removal of the entire colon is the only definite way to prevent colon cancer.