Anal Fistula

What is an anal fistula?

The anus is the external opening through which feces are expelled from the body. Just inside the anus are a number of small glands. If one of these glands become blocked, an abscess - an infected cavity - may form. An anal abscess is usually treated by surgical drainage, although some drain spontaneously. About 50% of these abscesses may develop into a fistula, in which a small tunnel connects the infected gland inside the anus to an opening on the skin around the anus.

What causes an anal fistula?

Most fistulas result from an anal abscess. A small number of fistulas may less frequently be caused by other processes such as Crohn’s disease, sexually transmitted diseases, trauma, tuberculosis, cancer, or diverticulitis.

What are the symptoms for an anal fistula?

The following may be symptoms or signs of an anal fistula:

• Recurrent anal abscesses
• Pain and swelling around the anus
• Pain with bowel movements
• Bleeding
• Bloody or foul-smelling drainage (pus) from an opening around the anus. The pain may decrease after the fistula drains
• Irritation of the skin around the anus due to persistent drainage
• Fever, chills, and a general feeling of fatigue. (However, these may be symptoms of many conditions)

You should see your physician if you notice any of these symptoms.

How is an anal fistula diagnosed?

Your physician can usually diagnose an anal fistula by examining the area around the anus. He or she will look for an external opening on the skin. If this is visible, your physician will then try to determine the depth and direction of the fistula tract. Often drainage can be produced from the external opening.

Some fistulas may not be visible on the skin’s surface. In this case, your physician may need to perform additional tests, starting with anoscopy, in which a special instrument is used to see inside your anus and rectum. Your physician may also order an ultrasound or MRI of the anal area to better define the fistula tract.

If a fistula is found, your physician may also want to do further tests to see if the condition is related to Crohn’s disease, an inflammatory disease of the intestine. About 25% of people with Crohn’s disease develop fistulas. Among these studies are blood tests, x-rays, and colonoscopy. A colonoscopy, in which a flexible, lighted instrument is inserted into the colon via the anus, is performed under conscious sedation, a type of light anesthetic.

What are the treatments for an anal fistula?

Surgery, performed by a colon and rectal specialist, is usually necessary to manage an anal fistula. During surgery, the physician will assess the depth and extent of the fistula tract. Most fistulas are treated with a fistulotomy, in which the skin and muscle over the tunnel are cut open, converting it into an open groove. This will allow the fistula tract to heal from the inside out. A more complex fistula may require placement of a special drain - a seton - for at least six weeks, after which a definitive surgical repair is done. Fistula surgery is generally done on an outpatient basis. Very large or deep fistula tunnels may require a short hospital stay.

Is any follow-up treatment necessary?

Following your fistula surgery, your physician may recommend soaking the affected area in a warm bath and taking stool softeners or laxatives for a week. Since you may also experience some pain or discomfort in the area after surgery, your physician will prescribe pain pills. Most fistulas respond well to surgical treatment.