What is a sigmoidoscopy, is it useful?

Sigmoidoscopy exam: The sigmoid colon is the last bend of the gut before food reaches the rectum. Accordingly, examination of the sigmoid ; left colon (hence the name "sigmoidoscopy") involves a flexible tube inserted into the rectum (often under sedation if you wish). The procedure takes only a few minutes ; typically requires only a limited preparation. On the other hand, "colonscopy" examines the whole colon.