Etiology and diagnosis of anal fissure and stenosis

Anal fissure is a linear crack of the anal mucosa between the dentate line and the mucocutaneous junction. The majority occur in the posterior midline, and usually can be diagnosed by patient history alone. The etiology of anal fissure is not well understood. The likely common factor is the passage of hard stool, resulting in a traumatic laceration. Theories of the etiology of anal fissure have focused on factors such the anatomical configuration of the sphincter muscles, elevated maximum anal resting pressure, infection, and most recently on the blood supply to the mucosa of the anal canal. Evidence that ischemia may be an important factor in the pathogenesis of anal fissure is the observation that reduction in sphincter pressure, produced by internal sphincterotomy, results in a corresponding increase in blood flow to the site of the fissure, which then heals. Anal stenosis is an abnormal narrowing of the anal canal. In the majority of cases, anal stenosis results from the removal of excessive amounts of tissue during anorectal surgery. Other conditions that have been associated with anal stenosis include chronic anal fissure, perianal sepsis, radiation, laxative abuse, and Crohn's disease.