Anal fistula

A short explanation for patients

An anal fistula is a small tunnel or connection which runs from the inside of the anus to the skin outside the anus. It is a common condition following an abscess. It is a nuisance because it causes recurring abscesses (boils or pimples). It is hardly ever dangerous. It can almost always be cured by an operation. A fistula seldom heals without an operation.

Most fistulas cross part of the anal sphincter muscle. This is the ring of muscle which keeps your anus closed. It allows you to control wind and bowel actions. To cure a fistula, the surgeon cuts the part of the sphincter muscle which is downstream of the fistula. This may affect your control of wind and bowel actions.

The cut at the anus is not stitched up. It is left to heal on its own. Often a small sample is examined under a microscope, to be sure that no cause for the fistula can be found. The cut is seldom very sore but it is always uncomfortable, being in a sensitive area. Most patients feel comfortable enough to go home on the day of the operation, although after a general anaesthetic you must not drive yourself home. If you feel sore or anxious you may prefer to spend a night in hospital, to be sure that strong pain-killers are available.

For the first day or two the cut produces a slightly bloody discharge. You will need a pad to absorb this. Having a bowel motion usually stings. After a motion, washing the anus is much more comfortable than wiping it, although water stings at first. A yellowish discharge continues for the first few weeks, then dries up. Sitting is usually uncomfortable rather than sore. Most patients return to work after about a week. Complete healing of the cut can take up to three months, although it causes little discomfort after the first few weeks.

To cure the fistula, it is almost always necessary to cut some of the anal sphincter muscle. This is only done after checking that most of the muscle will remain intact. Most patients find it harder to control wind after the operation. You should not agree to the operation unless you accept this. It is unusual to have trouble controlling runny bowel actions and it is rare for the operation to affect control of formed motions.

In a few patients, examination under anaesthesia shows that the fistula crosses a lot of the anal sphincter muscle. In this case, I do not cut any of the muscle. I feed a thin plastic tube, called a seton, through the fistula. The seton thus enters the opening of the fistula next to the anus, follows the fistula into the anal canal, and emerges through the opening of the anus. It is left in place until a decision is made on how to treat the fistula. A seton is usually uncomfortable, but seldom painful.

Occasionally the fistula is difficult to find. This is more common if you have had surgery for the same problem before. If so, the operation may not cure it, and further surgery may be needed later.