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Anal Fistula

symptoms, diagnosis, and treatment of anal fistulas

An anal fistula is an abnormal tunnel under the skin that connects the anal canal in the colon to the skin of the buttocks. Most anal fistulas form in reaction to an anal gland that has developed a pus-filled infection (abscess).


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

Who's at risk

If you develop an anal abscess, you have about a 50% chance of developing an anal fistula. Even if your abscess drains on its own, you have about the same risk for a fistula. Certain conditions that affect your lower digestive tract or anal area may also increase your risk. These include:

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


If you have symptoms that suggest an anal fistula, your healthcare provider may refer you to a specialist who specializes in colon and rectal diseases. The specialist will ask about your symptoms and your medical history. During your physical exam, the doctor will look for a fistula opening near your anal opening. He or she may press on the area to see if it is sore and if pus comes out. Different methods may be used to help with the diagnosis, such as:

  • 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 on the inside.
  • Anoscope. This is a special scope used to look inside your anal canal.
  • Imaging studies. 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.


Once you have an anal fistula, antibiotics alone will not cure it. You will need to have surgery to cure the fistula. Many surgical treatment options are available and you and your surgeon will discuss which one is appropriate for you. Surgical treatment options include:

  • Fistulotomy. This procedure opens up the fistula in a way that allows it to heal from the bottom up. It is usually used for simple fistulas that are close to the surface of the skin.
  • Rectal Advancement Flap. This procedure involves freeing a small portion of the top lining of the rectum and pulling it over and closing the internal fistula opening.
  • LIFT Procedure. Otherwise known as ligation of intersphincteric fistula tract and involves secure closing of the internal opening and removal of surrounding infected tissue via an incision next to the anus.
  • Filling the fistula with a special glue or plug. This treatment involves filling the fistula tunnel with a material that your body will absorb over time, closing the internal opening of the tract.
  • Seton placement. This procedure involves placing a suture or rubber band (seton) in the fistula that allows the tract to adequately drain and the associated inflammation to resolve. This procedure is often used as a first stage procedure in a two stage process. Once the inflammation goes away the fistula is now ready to have the seton removed and undergo a definitive repair procedure, such as those listed above, where the site will have a better chance of healing.

Note: 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.


Complications include a fistula that recurs after treatment and 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.

When to call the healthcare provider

Call your healthcare provider if you have symptoms of an anal fistula, especially if you have a history of a previous anal abscess. If you have been treated for an abscess or fistula, let your provider know right away if you have any of the following:

  • Fever
  • Chills
  • Redness
  • Swelling
  • Bleeding
  • Discharge
  • Constipation
  • Trouble controlling your bowel movements

Managing anal fistula

When recovering from anal fistula treatment, make sure to take pain medicine as directed by your surgeon. Finish all of your antibiotics. Don’t take any over-the-counter medicines without first talking to your provider.

Other important instructions may include:

  • Soaking in a warm bath 3 or 4 times a day
  • Wearing a pad over your anal area until healing is complete
  • Resuming normal activities only when you are cleared by your surgeon
  • Eating a diet high in fiber and drinking plenty of fluids
  • Using a stool softener or bulk laxative as needed
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