anal fissure

Anal fissures result from trauma to the anal canal, typically from passage of hard or large stool, leading to a tear in the squamous epithelium below the dentate line. The posterior midline is most commonly affected due to relatively poor perfusion in this watershed area supplied by the inferior rectal artery. Chronic fissures can lead to a cycle of pain, internal anal sphincter spasm, and decreased blood flow, perpetuating poor healing. This may result in a chronic fissure with a hypertrophied anal papilla proximally and a sentinel skin tag distally. Lateral or multiple fissures should raise suspicion for secondary causes such as Crohn disease, tuberculosis, syphilis, HIV, or anal carcinoma, since primary fissures are almost always posterior (or occasionally anterior) midline. Diagnosis is typically made by history and visual inspection, often without the need for digital rectal exam or anoscopy if pain is severe, as it can worsen sphincter spasm and patient discomfort. Treatment is initially conservative: high-fiber diet, stool softeners, increased fluid intake, warm sitz baths, and topical agents such as nitroglycerin or nifedipine (calcium channel blockers) to relax the internal anal sphincter and improve blood flow. Botulinum toxin injection is another option for chemical sphincter relaxation. Refractory cases may require lateral internal sphincterotomy, a surgical procedure that reduces sphincter tone and improves blood flow to promote healing. This is a common condition tested on Step 1/2 for differentiating from other anorectal disorders like hemorrhoids (usually painless bleeding unless thrombosed), anorectal abscess/fistula (associated with Crohn disease), and rectal prolapse.