A colonoscopy involves the insertion of a lighted flexible tube, called a colonoscope, into the rectum. The tube is inserted so that the lining of the colon is visualized. Any area of the lining that appears abnormal may be biopsied; that is, a piece of tissue may be removed for analysis. In addition, growths of the colon, called polyps, may be removed (polypectomy) by the use of an electrified wire, called a snare.

A colonoscopy is generally a safe procedure but in rare cases, complications from a colonoscopy may include: a reaction to the sedative used during the exam, a tear in the colon or rectum wall (perforation), or possible bleeding from the site where a tissue sample (biopsy) was taken.