There are many different types of fistula, ranging from a simple, singular tract to more complicated fistulas that can be made up of several tracts which branch out. Some fistulas can be connected to the muscles that control your bowels.

An anal fistula usually develops after an anal abscess (a collection of pus) bursts. It can also form when an abscess has not been completely treated.

They can also be caused by a condition which affects the intestines, such as irritable bowel syndrome or Crohn's disease.

Most anal fistulas require surgery, as they rarely heal if left untreated. However, complications are rare, and in most cases a fistula will not develop a second time.