Subscribe to our Living With Cancer e-newsletter to stay up to date on cancer topics. A colonoscopy (koe-lun-OS-kuh-pee) is an exam used to detect changes or abnormalities in the large intestine (colon) and rectum. During a colonoscopy, a long, flexible tube (colonoscope) is inserted into the rectum. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon. If necessary, polyps or other types of abnormal tissue can be removed through the scope during a colonoscopy.