A flexible sigmoidoscopy is an exam used to evaluate the lower part of the large intestine (colon). During a flexible sigmoidoscopy exam, a thin, flexible tube (sigmoidoscope) is inserted into the rectum.

A tiny video camera at the tip of the tube allows the doctor to view the inside of the rectum, the sigmoid colon and most of the descending colon — just under the last 2 feet (about 50 centimeters) of the large intestine. If necessary, tissue samples (biopsies) can be taken through the scope during a flexible sigmoidoscopy exam.

Flexible sigmoidoscopy doesn’t allow the doctor to see the entire colon. As a result, flexible sigmoidoscopy alone can’t detect cancer or small clumps of cells that could develop into cancer (polyps) farther into the colon.