A colonoscopy is a procedure that enables your physician to examine the entire length of the colon (approximately five feet) for abnormalities. This procedure is done by inserting a thin, flexible tube into the anus and advancing it slowing into the rectum and colon.
If the colonoscopy shows something abnormal, a forceps instrument is passed through the colonoscope to obtain a sample of the colon lining for further testing. These samples are taken for a number of reasons and does not necessarily mean that cancer is suspected.
Information adapted from the American Society of Gastrointestinal Endoscopy.