An anal fistula is a small channel that develops between the end of the bowel, known as the anal canal, and the skin near the anus.
The end of the fistula can appear as a hole in the skin around the anus. The anus is the opening where waste leaves the body.
Anal fistulas are usually classed as either:
What causes an anal fistula?
An anal fistula usually develops after an anal abscess (a collection of pus) bursts, or when an abscess has not been completely treated.
A fistula can also be caused by conditions that affect the intestines, such asinflammatory bowel disease (IBD)or diverticulitis.
An anal fistula affects:
Read more information about the causes of an anal fistula here.