Anal fissure
Anal fissure is a longitudinal tear of the anoderm distal to the dentate line that causes severe pain during and after defecation with bright-red bleeding, most often from hard stool passage and high internal sphincter tone. Diagnosis is clinical on gentle inspection, a posterior midline location is typical, and treatment steps from fiber and topical vasodilators to botulinum toxin and lateral internal sphincterotomy for disease refractory to medical therapy.
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What this article covers
- Overview
Definition: anal fissure is a longitudinal tear in the anoderm of the anal canal, distal to the dentate line, that does not extend beyond it.
- Epidemiology
Common anorectal complaint: one of the most frequent causes of anorectal pain and bleeding presenting to primary care and gastroenterology.
- Risk factors
Constipation and hard stool: the dominant risk factor, because passage of a large, hard bolus mechanically tears the anoderm.
- Pathophysiology
Initial mechanical tear: a hard stool bolus or other trauma tears the anoderm distal to the dentate line, most often posteriorly where perfusion of the anal canal is weakest.
- Clinical features
Severe anal pain with defecation: sharp, tearing pain during the bowel movement that characteristically persists for minutes to hours afterward, often worse than the stool passage itself.
- Differential diagnosis
Anorectal abscess: severe, constant perianal or rectal pain, often with fever, and an erythematous, indurated, or fluctuant mass rather than a visible linear tear (anorectal abscess).
- Diagnosis
This is a clinical diagnosis; direct visualization is the gold standard confirmatory step: gentle separation of the buttocks reveals a linear tear in the anoderm, most often in the posterior midline…
- Management
Start all patients on conservative first-line therapy, which heals most acute fissures within a few weeks: Increase dietary fiber to at least 25 g daily and add psyllium fiber supplement 5 g in water once to twice daily.
- Complications
Chronic non-healing fissure: the sphincter-spasm and ischemia cycle perpetuates the tear beyond 8 to 12 weeks, with edema, fibrosis, a sentinel tag, and a hypertrophied papilla.
- Prognosis
Acute fissures heal well: most resolve with fiber, fluids, sitz baths, and stool softeners alone within a few weeks.
- Prevention
Maintain adequate fiber intake: at least 25 to 30 g of dietary fiber daily, supplemented with psyllium if dietary intake is insufficient, to keep stool soft and bulky.
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