A patient who feels ill and complains of chills, fever and pain in the rectum or anus could be suffering from an anal abscess or fistula. These medical terms describe common ailments about which many people know little.

What is an anal abscess?

An anal abscess is an infected cavity filled with pus found near the anus or rectum.

What is an anal fistula?

An anal fistula is almost always the result of a previous abscess. Just inside the anus are small glands. When these glands get clogged, they may become infected and an abscess can develop. A fistula is a small tunnel that forms under the skin and connects a previously infected anal gland to the skin on the buttocks outside the anus.

What causes an abscess?

An abscess results from an acute infection of a small gland just inside the anus, when bacteria or foreign matter enters the tissue through the gland. Certain conditions – colitis or other inflammation of the intestine, for example – can sometimes make these infections more likely.

What causes a fistula?

After an abscess has been drained, a tunnel may persist connecting the anal gland from which the abscess arose to the skin. If this occurs, persistent drainage from the outside opening may indicate the persistence of this tunnel. If the outside opening of the tunnel heals, recurrent abscess may develop.