A colonoscopy is an examination of the large intestine, or colon, using a lighted, flexible endoscope.

It can be used to detect diverticulosis or an ulcer, and is known as the primary screening method for colorectal cancer.

Colonoscopy screening significantly improves colorectal cancer survival rates because it can detect tumors at an earlier, more treatable stage.

Colon cancer is one of the few cancers that can actually be prevented through screening because precancerous polyps, from which the cancers often develop, can be identified and removed.

According to the American Cancer Society, of all the people who were expected to die from colorectal cancer in 2008, appropriate testing could save more than half. The exam itself is routine and painless. However, your colon needs to be empty, so the day before the screening you will be asked to drink only clear fluids and you will  take a laxative.  

A sedative is given as part of the procedure, so you will need someone to drive you home. Consensus among the medical community is that people considered generally healthy have a colonoscopy by the age of 50.

Those considered high risk because of lifestyle or hereditary factors should consider earlier and more frequent screening.