An anal fistula usually develops as a result of an anal abscess which is drained or bursts. Around half of people who develop an anal abscess will go onto develop an anal fistula. An anal fistula is a track which forms between the inside of the anus and the skin on the outside. This track will continue to drain pus like material and occasionally faecal matter.
Once a fistula has formed it is very unlikely to heal without treatment. Anal fistulae may also develop as a result of other conditions such as Crohn’s disease
Symptoms of Anal Fistula
People suffering with an anal fistula will experience the following symptoms
- An opening may be seen or felt near to the anus
- Persisting discharge of pus and sometimes a little blood too
- Anal discomfort
- Skin irritation
The Surgeon will take a full history and carry out a clinical examination. Usually this will involve a rigid sigmoidoscopy and sometimes a proctoscopy as well. Often if the doctor is able find the inner and outer openings of the fistula and no special investigations will be required.
If it is not possible to find the fistula or if the problem is longstanding or recurrent, an MRI scan or endoanal ultrasound scan will be recommended.
Sometimes the area may be too uncomfortable to examine then the consultant may recommend carrying out an examination under anaesthetic to confirm the diagnosis, and if possible, the fistula can start to be treated at the same time.
If you are over the age of 40 and have had any bleeding or change in bowel habit the consultant may recommend endoscopic examination of the bowel either by flexible sigmoidoscopy. or colonoscopy to ensure that it is otherwise healthy, alongside treating the fistula
Anal Fistula Treatment
An anal fistula usually requires surgical treatment in order to heal. An anal fistula may often pass through the muscles surrounding the anus. These muscles are important for maintaining continence. It is very important that when fistulae are treated this muscle is not damaged excessively so that a patient has trouble controlling their bowels.
Fistula surgery can be difficult, and some patients may require repeated procedures in order to get their fistula healed.
Fistula surgery requires a general anaesthetic. There are several surgical options that can be used:
Seton Drainage: Simple drainage involves the insertion of a drainage tube known as a seton through the fistula track. This can stay in place long term but is frequently used for a few weeks only. This allows inflammation to settle, so that curative surgery can be planned
Laying open the fistula: This involves cutting out the fistula track. It is useful for those fistulae that don't pass through the sphincter muscle or only a small part of it.
Cutting Seton: This involves using a piece of tubing or seton which is placed through the fistula and tied firmly around the sphincter muscle. This tubing is tightened up every 2-3 weeks. Using this slow tightening technique, the fistula is gradually laid open. Sometimes three or more tightening are required.