A procedure in which a long flexible tube is inserted into the rectum. The tube has a light and video camera on the end of it, which allows view of the entire colon, and part of the small intestine. If needed, tissue biopsies of the inside of the colon can be taken, and polyps can be removed through the scope. The colon must be cleaned out before the procedure, to allow a good view of the colon. This is done by using a laxative, drinking liquids, and no food or drink for a number of hours before the colonoscopy.