The sigmoid colon is the part of the large intestine after the descending colon and before the rectum. The name sigmoid means S-shaped (see sigma). The walls of the sigmoid colon are muscular, and contract to increase the pressure inside the colon, causing the stool to move into the rectum.

Due to the intermittent high pressure within it, the sigmoid colon can develop pockets called diverticuli in its walls. The presence of diverticuli, whether harmful or not, is called diverticulosis. An infection of the diverticuli is called diverticulitis.

Sigmoidoscopy is a common diagnostic technique used to examine the sigmoid colon.

If long objects are inserted forcibly into the anus during anal sex, the sigmoid colon may be damaged.

Diseases

It is the most common site for colonic diverticula.