A colonoscopy is a procedure used to take a look or examine the inside of the large intestine, a.k.a. the colon and the rectum. It is commonly used on an outpatient basis and is used to identify causes behind gastrointestinal symptoms like intestinal and rectal bleeding, or issues with bowel movement and also to screen for cancer. During a colonoscopy, a long, flexible tube (colonoscope) is inserted into the rectum of the patient with a tiny video camera attached at the tip of the tube. The camera allows the doctor to view the inside of the entire colon and diagnose what is wrong with it.