Anal Fistula

What is an anal fistula?

The anal canal is the end part of the intestinal tract. It includes the rectum and anus. Sometimes an abnormal passage forms from the anal canal to the skin near the anus. This is called an anal fistula. Anal fistulas can also form from the anal canal to other organs, such as the vagina or urinary tract.

What causes an anal fistula?

An anal fistula most often happens from an anal gland that has developed a pus-filled infection (abscess). A fistula can also happen with certain conditions, such as Crohn’s disease. Or it may happen after radiation therapy for cancer. Injury to the anal canal and surgery can also cause anal fistulas.

Who is at risk for an anal fistula?

Having an anal abscess raises your risk of having an anal fistula. Certain conditions of the lower digestive tract or anal area may also raise your risk.

These include:

  • Colitis
  • Crohn’s disease
  • Chronic diarrhea
  • Radiation treatment for rectal cancer

What are the symptoms of an anal fistula?

The symptoms of an anal abscess and an anal fistula can be similar and may include:

  • Pain and swelling around the anal area
  • Fever and chills
  • Feeling tired and sick
  • Redness, soreness, or itching of the skin around the anal opening
  • Pus drainage near the anal opening

How is an anal fistula diagnosed?

If you have symptoms that seem like an anal fistula, you have to apply to a general surgeon. During your physical exam, the doctor will look for a fistula opening near your anal opening. They may press on the area to see if it’s sore and if pus comes out. Sometimes, you’ll need to have a special exam under anesthesia so the provider can get more information without causing you pain. Different methods may be used to help with the diagnosis.

These include:

Fistula probe:

A long, thin probe is guided through the outer opening of the fistula. A special dye may be injected to find out where the fistula opens up.


This is a special scope used to look inside your anal canal.

Imaging tests:

These may include an ultrasound, which creates an image of the anal area using sound waves. Or they may include an MRI, which makes images of the area by using special magnets and a computer.

How is an anal fistula treated?

Once you have an anal fistula, antibiotics alone won’t get rid of it. You’ll need to have surgery to treat the fistula. Surgical treatment includes:


This procedure opens up the fistula in a way that lets it heal from the inside out. It’s usually an outpatient procedure. This means you go home the same day.

Filling the fistula with a special glue or plug:

This is a newer type of treatment that closes the inner opening of the fistula. The provider then fills the fistula tunnel with a material that your body will absorb over time.

Reconstructive surgery or surgery that is done in stages:

This may be an option in some cases.

Seton placement:

This procedure places a suture or rubber band (seton) in the fistula that is slowly tightened. It lets the fistula drain and heal behind the seton. It lowers the risk for incontinence.

Laser therapy:

Laser technology is used to close the fistula tunnel.

Anal fistulas are very common in people with Crohn’s disease. For those with both Crohn’s disease and a fistula, medical therapy is often tried before surgery.

What are the possible complications of an anal fistula?

Complications of an anal fistula include that it may return after treatment. Another complication is an inability to control bowel movements (fecal incontinence). This is most likely if some of the muscle around the anal opening, called the anal sphincter, is removed.

Talk with your healthcare provider about the risks, benefits, and possible side effects of all treatments.