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

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.

An abscess is treated by making an opening in the skin near the anus to drain the pus from the infected cavity and thereby relieve the pressure. A large or deep abscess may require hospitalization and the assistance of an anesthesiologist. Hospitalization may also be necessary for patients prone to more serious infections, such as diabetics or people with decreased immunity. Antibiotics are a poor alternative to draining the pus, because antibiotics do not penetrate the fluid within an abscess.