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Anorectal Fistula

(Fistula in Ano)


Parswa Ansari

, MD, Hofstra Northwell-Lenox Hill Hospital, New York

Last full review/revision Feb 2021| Content last modified Feb 2021

An anorectal fistula is a tubelike tract with one opening in the anal canal and the other usually in the perianal skin. Symptoms are discharge and sometimes pain. Diagnosis is by examination and sometimes anoscopy, sigmoidoscopy, or colonoscopy. Treatment often requires surgery.

(See also Evaluation of Anorectal Disorders.)

Fistulas arise spontaneously or occur secondary to drainage of a perirectal abscess. Most fistulas originate in the anorectal crypts. Other causes include

Fistulas in infants are congenital and are more common among boys.

Rectovaginal fistulas may be secondary to Crohn disease, obstetric injuries, radiation therapy, or cancer.

Symptoms and Signs of Anorectal Fistula

A history of recurrent anorectal abscess followed by intermittent or constant discharge is usual. Discharge material is purulent, serosanguineous, or both. Pain may be present if there is infection. On inspection, one or more secondary openings can be seen. A cordlike tract can often be palpated. A probe inserted into the tract can determine the depth and direction and often the primary opening.

Diagnosis of Anorectal Fistula

  • Clinical evaluation
  • Sometimes anoscopy, sigmoidoscopy, or colonoscopy

Diagnosis of anorectal fistula is by examination. Anoscopy or sigmoidoscopy may be used to visualize the internal opening of the fistula. Colonoscopy should follow if there is suspicion of Crohn disease (see diagnosis of Crohn disease).

Hidradenitis suppurativa, pilonidal sinus, dermal suppurative sinuses, and urethroperineal fistulas must be differentiated from cryptogenic fistulas.

Treatment of Anorectal Fistula

  • Various surgical procedures
  • Medical treatment if caused by Crohn disease

(See also the American Society of Colon and Rectal Surgeons' clinical practice guideline for the management of anorectal abscess, fistula-in-ano, and rectovaginal fistula.)

In the past, the only effective treatment was surgery, in which the primary opening and the entire tract are unroofed and converted into a “ditch.” Partial division of the sphincters may be necessary. Some degree of incontinence may occur if a considerable portion of the sphincteric ring is divided. Alternatives to conventional surgery include advancement flaps, biologic plugs, and fibrin glue instillations into the fistulous tract. More recently, the ligation of intersphincteric fistula tract (LIFT) procedure, where the fistula tract is divided between the sphincter muscles, has gained acceptance as an alternative more likely to preserve continence.

If diarrhea or Crohn disease is present, fistulotomy is inadvisable because of delayed wound healing. For patients with Crohn disease, metronidazole, other appropriate antibiotics, and suppressive therapies can be given (see treatment of Crohn disease). Infliximab is effective in closing anal fistulas caused by Crohn disease.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  • American Society of Colon and Rectal Surgeons: Clinical practice guideline for the management of anorectal abscess, fistula-in-ano, and rectovaginal fistula

Drugs Mentioned In This Article

Drug Name Select Trade
metronidazole FLAGYL
Infliximab REMICADE

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