(See also Evaluation of Anorectal Disorders.)
Anal fissures are believed to result from laceration by a hard or large stool or from frequent loose bowel movements. Trauma (eg, anal intercourse) is a rare cause. The fissure may cause internal sphincter spasm, decreasing blood supply and perpetuating the fissure.
Anal fissures usually lie in the posterior midline but may occur in the anterior midline. Those off the midline may have specific etiologies, particularly Crohn disease. An external skin tag (the sentinel pile) may be present at the lower end of the fissure, and an enlarged (hypertrophic) papilla may be present at the upper end.
Fissures cause pain and bleeding. The pain typically occurs with or shortly after defecation, lasts for several hours, and subsides until the next bowel movement. Examination must be gentle but with adequate spreading of the buttocks to allow visualization.
Infants may develop acute fissures, but chronic fissures are rare.
(See also the American Society of Colon and Rectal Surgeons’ clinical practice guideline for the management of anal fissures.)
Fissures often respond to conservative measures that minimize trauma during defecation (eg, stool softeners, psyllium, fiber). Healing is aided by use of protective zinc oxide ointments or bland suppositories (eg, glycerin) that lubricate the lower rectum and soften stool. Topical anesthetics (eg, benzocaine, lidocaine) and warm (not hot) sitz baths for 10 or 15 minutes after each bowel movement and as needed give temporary relief.
Topical nitroglycerin 0.2% ointment, nifedipine cream 0.2%, 2% diltiazem gel, and injections of botulinum toxin type A into the internal sphincter relax the anal sphincter and decrease maximum anal resting pressure, allowing healing. When conservative measures fail, surgery (internal anal sphincterotomy) is needed to interfere with the cycle of internal anal sphincter spasm.