Overview

A flexible sigmoidoscopy (sig-moi-DOS-kuh-pee) 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.

Why it's done

Your doctor may recommend a flexible sigmoidoscopy exam to:

• Investigate intestinal signs and symptoms. A flexible sigmoidoscopy exam can help your doctor explore possible causes of abdominal pain, rectal bleeding, changes in bowel habits, chronic diarrhea and other intestinal problems.
• Screen for colon cancer.If you're age 50 or older and you have no colon cancer risk factors other than age — which puts you at average risk — your doctor may recommend a flexible sigmoidoscopy exam every five years to screen for colon cancer. Sigmoidoscopy is one option for colon cancer screening, but there are other options that allow your doctor to view your whole colon, such as colonoscopy. Talk with your doctor about your options.
• Sigmoidoscopy may occasionally be preferred over colonoscopy because the preparation for sigmoidoscopy and the test itself may take less time. In addition, an anesthetic is often not required. There is a lower risk of direct harm such as a tear in the colon or rectum wall (perforation) with sigmoidoscopy, compared with colonoscopy.