A colonoscopy is a procedure that allows a physician to examine the inner lining of the large intestine, according to WebMD. Using an instrument called a colonoscope, the doctor examines the rectum and colon for signs of ulcers, polyps, tumors, inflammation or bleeding.
A colonoscope is a thin, flexible tube with a small video camera attached. For the colonoscopy to be effective, the patient must clean out the colon beforehand. This preparation process normally takes one to two days and often involves drinking a solution that induces frequent bowel movements. For this reason, it is best not to leave home while preparing for the procedure, WebMD advises.