Anal Fistula & Abscess

The commonest cause of an anal fistula is an anal abscess  An abscess is a collection of infected pus and fluid. An anal abscess is usually caused by an infected gland just inside the anus. The infection can spread either downwards around the anus leading to a painful, tender swelling, called a perianal abscess, or outwards into the surrounding fat, known as an ischiorectal abscess, resulting in throbbing pain, fever and malaise. Surgical treatment is usually required to incise and drain the abscess.

In about a third of patients the abscess does not heal completely resulting in an anal fistula. A fistula is a persistent channel between the infected gland and the skin resulting in an intermittent pus discharge. The fistula can be 'low' or 'high' depending on the degree of involvement of the sphincter muscle. Surgical treatment is often required.