Anal Fistula

What is an Anal Fistula?

When one of the small glands within the anus becomes blocked, it’s referred to as an anal fistula. It’s often caused by a previous or existing abscess (a swollen area often filled with fluid or pus) in the anus. Some anal fistulas will heal naturally while others require surgery to drain the fluid.

Why Anal Fistulas Develops

Approximately half of all anal abscesses eventually become anal fistulas. Sexual transmitted diseases, injury or trauma, and some forms of cancer can also increase the risk of developing a fistula.

What are the Symptoms of Anal Fistula?

Diagnosing an Anal Fistula

A physical exam is the first step in diagnosing an anal fistula. If there are no visible signs of one, an anoscope (special instrument to view inside of the rectum) may be used to confirm if an anal fistula is present.

Symptoms include

  • Pain during bowel movements
  • Anal swelling and discomfort
  • Pus around the anus
  • Anal skin irritation
  • Increased fatigue
  • Fever

Anal Fistula Causes

Anal fistulas occur as a result of an infection in the area between the end of the bowel and the skin around the anus. During the infection, pus collects in a tunnel in the tissues. When the pus is drained away, the tunnel is then left behind – this is a fistula.

Infections in this area tend to be anal abscesses. Usually, abscesses are caused by infections of the internal glands found around the anus. Fecal matter, bacteria or foreign material can sometimes clog these glands. The body then attempts to fight off the infection by creating pus, which causes the filled cavity.

Usually, anal abscesses are treated by making a small incision near the anus and draining the infection. Although often the empty cavity will then heal correctly on its own, sometimes the tunnel created by the infection remains and this can then become infected again and again.

In rare instances, anal fistulas can be caused by conditions other than abscesses.

Some of the less common causes of fistulas include:

  • Crohn’s disease (an inflammatory bowel condition)
  • Hidradenitis suppurativa (a skin condition)
  • Diverticular disease (a condition affecting the colon)
  • Infection caused by TB or HIV
  • Complications of surgery near the anus

How is an Anal Fistula Treated?

Treatment includes

Surgery is often recommended is an anal fistula hasn’t drained on its own. The most common surgical procedure to treat an anal fistula is a fistulotomy. It involves the creation of an open space along the fistula tract. During the procedure, the surgeon will explore the tract to determine if other glands are also affected. A drainage device may be inserted for six weeks before proceeding with surgical repair. Performed under general anesthesia, the application of fibrin glue is the only non-surgical remedy.

Surgery risks include

  • Bowel incontinence
  • Recurrence of anal fistulas
  • Infection

After initial treatment, patients are usually instructed to use stool softeners for about a week and take warm baths. Pain medications may be prescribed if discomfort continues during the initial healing process after surgery. Most fistulas respond well to treatment.

Anal Fistula Prevention

Since most anal fistulas are caused by anal abscesses, preventing abscesses should come first. Often, anal abscesses occur for reasons completely beyond our control, but staying clean and hygienic in the anal area may help to prevent them.

Since STIs may be responsible for some anal abscesses, it is incredibly important to wear a condom during anal intercourse and undergo frequent sexual health screenings.

Not all anal abscesses result in anal fistulas, but seeking treatment as early as possible might help to reduce the risk of a fistula. By understanding the signs and symptoms of anal abscesses and infections you can catch the condition early and perhaps prevent the development of a fistula.

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Last Reviewed:
September 12, 2016
Last Updated:
June 08, 2018