Diverticulum: A small bulging sac pushing outward from the colon wall is a diverticulum. As a person ages, pressure within the large intestine (colon) causes pockets of tissue (sacs) that push out from the colon walls. The plural is diverticula. Diverticula can occur throughout the colon but are most common near the end of the left side of the colon, the sigmoid colon.
