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 and extend to the perianal skin. Other causes include
Cancer
Trauma
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
Fistulotomy or fistulectomy, in which the primary opening and the entire tract are unroofed and converted into a “ditch,” is sometimes performed. Partial division of the sphincters may be necessary. Some degree of incontinence may occur if a considerable portion of the sphincteric ring is divided (1).
Alternative treatments include biologic plugs and fibrin glue instillations into the fistulous tract, but these procedures have low success rates. The endorectal advancement flap, a procedure to cover the internal opening of the fistula with a flap of tissue from the rectum, avoids cutting the sphincter muscle and has reasonable healing rates. The ligation of intersphincteric fistula tract (LIFT) procedure, in which the fistula tract is divided between the sphincter muscles, is an alternative more likely to preserve continence.
If diarrhea or Crohn disease is present, fistulotomy is inadvisable because of delayed wound healing and of the potential for fecal incontinence.
For patients with Crohn disease, metronidazole, other appropriate antibiotics, and suppressive therapies can be given (see For patients with Crohn disease, metronidazole, other appropriate antibiotics, and suppressive therapies can be given (seetreatment of Crohn disease). Infliximab is effective in closing ). Infliximab is effective in closinganal fistulas caused by Crohn disease.
Treatment reference
1. Gaertner WB, Burgess PL, Davids JS, et al. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Anorectal Abscess, Fistula-in-Ano, and Rectovaginal Fistula. Dis Colon Rectum. 2022;65(8):964-985. doi:10.1097/DCR.0000000000002473
