Colonoscopy is an exam of the inner lining of the rectum and colon, using a colonoscope, which is a long, flexible tube with a camera on the end. It is a simple test used to detect the presence of a number of diseases like colon cancer and other conditions of the intestines, as well as to treat and remove polyps. During the test tissue samples are often collected, biopsied and any abnormal growths can be removed.