Anal fistula

What is an anal fistula?

An anal fistula is small channel or tunnel that develops between the end of the bowel and the skin near the anus (i.e. where stool leaves the body). These can result in bleeding when passing stool and cause pain and discomfort. Often anal fistulas won’t get better on their own and will usually require treatment. Surgery is a common recommendation for treating anal fistulas.

What are the symptoms of an anal fistula?

The most common symptoms of an anal fistula are:

  • pain where the fistula is, which can be made worse when sitting down or passing stool
  • passing pus or blood 
  • skin irritation around the anus
  • fever

What causes an anal fistula?

Anal fistulas are usually a result of an anal abscess that has not healed properly. When an anal abscess has not healed properly, the pus has drained away, but leaves a channel or tunnel behind. It is common for an anal abscess to result in anal fistula.

Other causes of anal fistulas include:

  • surgical complication near the anus
  • Crohn’s disease
  • diverticulitis

What is the treatment for an anal fistula?

As anal fistulas usually do not heal on their own, surgery is often required. There are numerous types of surgery, including:

  • Fistulotomy – the length of the fistula is cut open so that the contents can be removed. Once healed, a flat scar is left behind.
  • Seton procedures – surgical thread (a seton) is placed into the fistula and left there for a few weeks. This helps it to heal before another procedure is performed to treat it fully.
  • Fibrin glue – a non-surgical treatment option that involves glue being injected into the fistula to seal the channel, with the opening stitched shut. However, long-term results with this procedure are not as successful with further surgery being required in many cases.
  • Flap procedures – often used in more complex cases, a piece or flap of tissue from skin around the anus is removed. The fistula tract is also removed and the flap if reattached where the fistula opening was.