An anal fistula is a small tunnel that connects an abscess, an infected cavity in the anus, to an opening on the skin around the anus. The anus is the external opening through which feces are expelled from the body. Just inside the anus are a number of small glands that make mucus. Occasionally, these glands get clogged and can become infected, leading to an abscess. About half of these abscesses may develop into a fistula. The leading causes of an anal fistula are clogged anal glands and anal abscesses.
Anal Fistula | Johns Hopkins Medicine
Anal fistula is a chronic abnormal communication between the epithelialised surface of the anal canal and usually the perianal skin. They can form when anal abscesses do not heal properly. Anal fistulae originate from the anal glands , which are located between the internal and external anal sphincter and drain into the anal canal. The tract formed by this process is a fistula.
The majority are associated with anorectal abscess formation, with one third of patients with an anorectal abscess having an associated perianal fistula at the time of presentation. The formation of an perianal fistula typically occurs as a consequence of an perianal abscess. However, other risk factors for their formation include:. Anal fistulae usually present with either 1 recurrent perianal abcesses 2 intermittent or continuous discharge onto the perineum , including mucus, blood, pus, or faeces. Figure 1 — The Goodsall rule, used clinically to predict the course of a fistula tract.
Most anal fistulas form in reaction to an anal gland that has developed a pus-filled infection abscess. Even if your abscess drains on its own, you have about the same risk for a fistula. Certain conditions that affect your lower digestive tract or anal area may also increase your risk. These include:.