An anorectal fistula is an abnormal channel that leads from the anus or rectum usually to the skin near the anus but occasionally to another organ, such as the vagina.

• Anorectal fistulas are common among people who have an anorectal abscess, Crohn's disease, or tuberculosis.
• Anorectal fistulas can cause pain and produce pus.
• The diagnosis is based on an examination and other viewing techniques.
• Treatment nearly always involves surgery, but some less invasive alternatives now exist.

Most fistulas begin in a deep gland in the wall of the anus or rectum. Sometimes fistulas occur after drainage of an anorectal abscess, but often the cause cannot be identified. Fistulas are more common among people with Crohn's disease or tuberculosis. They also occur in people with tumors, diverticulitis, cancer, or an anal or rectal injury. A fistula in an infant is usually a birth defect and is more common among boys than girls. Fistulas that connect the rectum and vagina may result from radiation therapy, cancer, Crohn's disease, or an injury to a mother during childbirth.

Symptoms and Diagnosis

An infected fistula may be painful and may discharge pus.

A doctor can usually see one or more openings of a fistula or can feel the fistula beneath the surface. A probe may be inserted to determine its depth and direction. Looking through an anoscope (a short, rigid tube) inserted into the rectum and exploring with the probe, a doctor may locate the internal opening. Inspection with a sigmoidoscope, which is a much longer viewing scope, helps a doctor determine whether the problem is being caused by cancer, Crohn's disease, or another disorder.

Treatment

Previously, the only effective treatment was surgery to open the fistula (fistulotomy). During surgery, sometimes the sphincter is partially cut. If too much of the sphincter is cut, the person may have difficulty controlling bowel movements. Newer surgical procedures use advancement flaps (flaps are stretched over the opening of the fistula) or other procedures to close the internal opening of the fistula. Biologic plugs and fibrin glue instillations are alternatives to fistulotomy.

If the person has diarrhea or Crohn's disease, which may delay wound healing, surgery usually is not performed. Drug treatment for Crohn's disease (see Inflammatory Bowel Diseases (IBD): Prognosis and Treatment) can help a fistula close.

Last full review/revision May 2012 by Parswa Ansari, MD