A colonoscopy is an endoscopic procedure where a long, thin, flexible camera is placed into the rectum and advanced through the entire colon (large intestine). The camera has a light on the end of it which allows the physician to examine the lining of the colon. A colonoscopy may be performed to diagnose the cause of gastrointestinal symptoms such as diarrhea, bleeding, abdominal pain, or abnormal x-ray results. A colonoscopy may also be performed on an asymptomatic patient at age 50, or sooner depending on the patient’s history, to screen for colon cancer and polyps. If colon polyps are found at early enough stage, they can be removed on the spot.