A colonoscopy is a test that looks for changes in the large intestine (colon) and rectum, such as swollen, irritated tissues, polyps, or cancer.
A long, flexible tube (colonoscope) is inserted into the rectum during a colonoscopy. The doctor can see the inside of the colon thanks to a tiny video camera at the tip of the tube.
Polyps and other types of abnormal tissue can be removed through the scope during a colonoscopy if necessary. Tissue samples (biopsies) can also be obtained during a colonoscopy.