Introduction

An anal fistula is a small tunnel that develops between the end of the bowel and the skin near the anus (where poo leaves the body).

They are usually the result of an infection near the anus causing a collection of pus (abscess) in the nearby tissue. When the pus drains away, it can leave a small channel behind.

Anal fistulas can cause unpleasant symptoms, such as discomfort and skin irritation, and won't usually get better on their own. Surgery is recommended in most cases.

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Medically Reviewed by a doctor on 30 Nov 2016