Introduction
An anal fistula is where a small tunnel (the Latin word 'fistula' means 'pipe') develops between the lining of the anal canal and the surface of the skin. Sometimes a fistula takes the form of one 'tunnel' and in other cases a number of these tunnels can develop. An anal fistula can interrupt the proper functioning of the muscles that control the bowel.
Symptoms
The main symptom of an anal fistula is weeping of blood or fluid (often foul smelling) from an opening in the skin near the anus. Where the fistula has not yet broken through the skin, other symptoms may indicate the presence of a fistula, such as:
- Pain / swelling / irritation in the anal area.
- Painful bowel movements.
- Tiredness / chills / fever.
- Recurring anal abscesses.
Causes
Around half of all anal fistulae develop from the site of an existing or previous anal abscess where anal glands have become blocked and infected. Anal glands are located near the anal opening and produce mucus to help with bowel movements. More rarely, an anal fistula may also be caused by:
- Cancer.
- Crohn's disease.
- Injury (including from radiation treatment for cancer).
- Sexually transmitted diseases.
- Tuberculosis.
Tests & Diagnosis
The first step is an examination of the anal area, usually under an anaesthetic. If a fistula is confirmed, it is important to determine how much of the anal muscles (sphincter muscles) the fistula crosses and whether the fistula branches. A colonoscopy may also be required to ensure there are no other causes for the development of a fistula, most importantly Crohn's disease or cancer. With complex fistulas, an MRI scan may be required to give a “road-map” of the fistula and its characteristics.
Treatment
The only effective treatment for anal fistula is anal fistula surgery. The treatment is determined by the cause. Once other important causes are excluded, the fistula can be treated by in a variety of ways, including:
- ‘Laying open’ – converting the tunnel into a flat bed.
- LIFT (ligation of intersphincteric fistula tract) procedure – disconnecting the tunnel.
- Flaps.
- Fistula plugs and glues.
In some cases, a temporary elastic tape, or seton, may be placed through the fistula tunnel, if it cannot be layed open. This allows the tunnel to become more rigid, to allow a further procedure to be performed more easily.
