A colonoscopy (koe-lun-OS-kuh-pee) is an exam used to look for changes — such as swollen, irritated tissues, polyps or cancer — in the large intestine (colon) and rectum.

During a colonoscopy, a long, flexible tube (colonoscope) is inserted into the rectum. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon.

If necessary, polyps or other types of abnormal tissue can be removed through the scope during a colonoscopy. Tissue samples (biopsies) can be taken during a colonoscopy as well.