An anal fistula is an inflammatory tract between the anal canal and the skin. The four categories of fistulas, based on the relationship of fistula to sphincter muscles, are intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric.
Anal fistulas are a complication of anorectal abscesses, which are more common in women than in men. Anal fistula forms in approximately 30%-50% of patients with anorectal abscess, and the vast majority of anal fistulas arise from anorectal infection.
A patient with an anal fistula may complain of recurrent malodorous perianal drainage, pruritus, recurrent abscesses, fever, or perianal pain due to an occluded tract. Patients may report a recent perianal or buttock abscess. Pain occurs with sitting, moving, defecating, and even coughing. It usually is throbbing in quality and is constant throughout the day. Pain occasionally resolves spontaneously with reopening of a tract or formation of a new outflow tract.
Bidigital rectal examination in a patient with an anal fistula may reveal an indurated tract or cord. A fistula can be identified by small circles of granulation tissue, which exude pus when compressed if the tissue is patent. A fistulous tract that opens internally can be visualized with the aid of an anoscope. Inguinal lymph nodes may be enlarged and painful. If an abscess is also present with an anal fistula, the cardinal signs of inflammation, rubor, dolor, calor, and tumor (eg, erythema, pain, increased temperature, and edema) may be found.
Treatment of anal fistulas depends on (1) the location of the fistula, (2) evidence of sepsis or a large abscess, or (3) worrisome findings on physical examination. If an abscess is present, drainage is indicated. Antibiotics should be reserved for patients with overlying cellulitis or those with sepsis. Otherwise, symptomatic treatment with analgesics should be considered.
Outpatient follow-up with a surgeon is indicated if consultation did not take place at the time of presentation. Surgical therapy is often indicated for healing of an anal fistula. The surgical approach depends on whether the fistula is simple or complex, as well as the risk for complications, such as incontinence.
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Cite this: Richard H. Sinert. Fast Five Quiz: Anal Conditions - Medscape - Mar 26, 2021.