Anal Fistula

What is an anal fistula?

An anal fistula is an abnormal tunnel connecting your anal canal with the skin around your anus. Most anal fistulas occur because of an anal abscess.

Anal fistulas don’t usually get better on their own. Most need surgical treatment.

What are the symptoms of an anal fistula?

Symptoms of an anal fistula include:

  • pain around the anus, which may be worse when you sit down, move around or pass a bowel motion
  • irritation of the skin around the anus
  • a discharge from near your anus (this can be pus or blood and might smell bad)
  • swelling and redness around your anus
  • fever (if you have an anal abscess).

A hole in the skin near your anus might be visible. But it’s difficult to see this for yourself.

What causes an anal fistula?

The most common cause is an anal abscess. When the pus drains from the abscess, it can leave a small tunnel behind. This can continue to drain or it can close over, which leads to recurrent anal abscesses. About half of the people who develop an anal abscess with also develop a fistula.

There are some other less common causes such as:

  • Crohn’s disease
  • Hidradenitis suppurativa – a chronic skin condition involving abscesses and scarring
  • HIV infection
  • Complications of childbirth or of anal surgery.

How is an anal fistula diagnosed?

Anal fissures can usually be diagnosed during physical examination. The physical examination involves gently parting your buttocks to see the anal area and a digital rectal examination. This is where your doctor inserts a gloved, lubricated finger into the anal canal and feels for anything abnormal.

Because there are several causes, your doctor may also check for:

  • Crohn’s disease
  • diverticular disease
  • sexually transmitted infections.

Your doctor may also arrange for an ultrasound, CT or an MRI.

How is are anal fistulas treated?

Anal fistulas usually need surgery to heal.

The surgery options include:

  • fistulotomy – where the whole length of the fistula is opened so that it heals into a flat scar after around 2 months
  • seton procedures – where some surgical thread (called a seton) is placed in the fistula and left there for several weeks. This helps healing before other procedures are done
  • advancement flap procedures – where the fistula is removed and a flap of tissue from the rectum or anus is attached to where the fistula was
  • bio prosthetic plug – where a cone shaped plug made of human tissue is used to block the internal opening of the fistula. New tissue usually grows around the plug to heal the fistula.

There is one non-surgical option. It involves injecting a special glue into the fistula. Although it’s considered non-surgical, the procedure does involve some stitches to close the opening of the fistula.

Your anal fistula specialist will discuss with you what the best options are for your situation.