All procedures carry some risk. Fortunately, the occurrence of major complications is very low in this procedure. The potential major complications include severe bleeding or possibly perforation of the colon. This occurs less than one in a thousand cases. If biopsies or polypectomies (removal of polyps) are preformed, the risk may increase. You will be given intravenous sedation (usually Demerol and Versed) before the procedure. This will help with the discomfort that may be left when advancing the colonoscope around the colon. There is a small chance (10-15%) that the entire colon cannot be examined. This is generally seen in patients who have had previous abdominal surgery or who have severe diverticulosis. In this case, a follow-up barium enema may be ordered.