Diverticula are small, balloon-like pouches that protrude from the intestines. This is a condition called diverticulosis. Although they can form throughout the colon, they are most often found in the sigmoid colon (the portion of the large intestine closest to the rectum). 

Anal cancer is the abnormal growth of cells in the anus, which is the opening at the end of the rectum where stool leaves the body. Anal cancer is uncommon and is often curable. Like other cancers, it can metastasize to other parts of the body, commonly the liver and lungs, although spreading is rare.

Small glands are located inside the anus. In some cases, these glands can become blocked and the cavity infected. This is known as an anal abscess, which has a fifty percent chance of becoming an anal fistula. The abscess drains through the skin next to the anus. The fistula then forms a tunnel under the skin and connects with the infected gland.