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Anorectal fistula: Clinical manifestations, diagnosis, and management principles

Section Editor
Martin Weiser, MD
Deputy Editor
Wenliang Chen, MD, PhD


An anorectal fistula is the chronic manifestation of the acute perirectal process that forms an anal abscess [1]. When the abscess ruptures or is drained, an epithelialized track can form that connects the abscess in the anus or rectum with the perirectal skin [2]. Anal fistulas are sometimes also referred to as "fistula-in-ano."


The true prevalence of anal fistulas is unknown, as anorectal discomfort is often attributed to symptomatic hemorrhoids. The incidence of an anal fistula developing from an anal abscess ranges from 26 to 38 percent [3-5]. The mean age for presentation of anal abscess and fistula disease is 40 years (range 20 to 60) [6-9]. Adult males are twice as likely to develop an abscess and/or fistula compared with women [1,9].


The most common etiology of an anorectal fistula is an infected anal crypt gland. Other causes include:

Crohn disease – Fistulas complicating Crohn disease or other intra-abdominal inflammatory processes may be accompanied by associated bowel symptoms such as diarrhea and abdominal pain. Anorectal fistulas preceding other clinical manifestations of Crohn disease are uncommon. As an example, in one surgical series of 136 patients with Crohn disease, fistulas preceded the intestinal manifestations of the disease in only six patients (5 percent) [10]. (See "Perianal complications of Crohn disease", section on 'Perianal fistula'.)

Lymphogranuloma venereum – Lymphogranuloma venereum is a chronic infection in the lymphatic system caused by Chlamydia trachomatis and can cause inflammatory perirectal masses. (See "Lymphogranuloma venereum".)

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Literature review current through: Nov 2017. | This topic last updated: Nov 16, 2017.
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