The word 'fistula' (which means a 'pipe' or 'ulcer' in Latin) describes an abnormal 'tunnel' between organs in the body or connecting to the outside through the skin. Although a fistula can present anywhere in the body, they occur most frequently in the digestive tract and an anal fistula is one that appears near the anus.
Anal fistulas (also called 'fistula in ano') are generally caused by an abscess - i.e. the collection of pus as a result of an acute infection - the pus tries to find a way to drain and creates an abscess, which then attempts to drain by creating a tunnel - the fistula.
Fistulas are common in young adults although may present at any age. The three major risk factors for fistulas are Crohn's Disease, smoking and having had previous anal abcesses or fistulas.
The main symptom of anal fistula is pain in, or inflammation of, an area near the anus, often combined with a discharge of foul smelling pus. Other symptoms may also appear, such as fever or bleeding from the anus or difficulty or pain urinating.
Some form of surgery is normally required to correct anal fistulas.
If the fistula is in the lower sphincter muscles, the fistula can be cut away to allow healthy tissue to heal the wound. Where the fistula passes through upper sphincter muscles, surgery is generally performed to allow the fistula to drain properly by inserting a device called a 'seton', which is made out of rubber or suture material, into the fistula. A seton will remain in place for anything up to three months, at which point a number of surgical options can be considered to treat the fistula.
Most surgery for anal fistula can be carried out as day surgery, i.e. with no stay in hospital required.