A sigmoidoscopy is a way to view the lower 20 inches of a patient’s sigmoid colon and rectum. The sigmoid colon and rectum are part of the large intestine. The large intestine helps the body process waste. The first 5 to 6 feet of the large intestine is the colon. The last 6 inches of the large intestine is the rectum, ending at the anus.

A sigmoidoscopy is done with a device called a sigmoidoscope. A sigmoidoscope is a pencil thin, flexible tube with a light and a camera on the end. During a sigmoidoscopy, the doctor inserts the sigmoidoscope into the anus, through the rectum, and into the lower part of the colon. The doctor views the inside of the colon through the scope or on a video monitor.

Doctors often use this exam to screen for colorectal cancer or intestinal polyps. Polyps are small abnormal growths that may become cancerous. They also use it as a diagnostic test for patients who have rectal bleeding, a change in bowel habits, or other symptoms.
A doctor can also remove small growths and collect tissue samples (biopsy) through a sigmoidoscope.

Preparation for the test includes emptying the bowels ahead of time using a laxative or enema.