Anal Fissure

Definition

An anal fissure is a linear tear or ulceration in the distal anal canal, usually posterior midline, causing pain during defecation and bleeding.

Epidemiology

• Common anorectal disorder, affecting all age groups
• Acute fissures often heal spontaneously; chronic fissures persist beyond 6–8 weeks
• Slightly more common in young adults
• Equally prevalent in males and females
• Higher prevalence in patients with constipation or inflammatory bowel disease

Etiology

• Trauma from passage of hard or large stools
• Chronic constipation or straining
• Diarrhea causing repeated irritation
• Anal intercourse or trauma
• Underlying conditions: Crohn’s disease, HIV, tuberculosis, malignancy
• Spasm of internal anal sphincter contributing to ischemia

Pathophysiology

• Mechanical trauma leads to linear tear in anoderm
• Persistent internal anal sphincter hypertonia → reduced blood flow → impaired healing
• Inflammatory response in chronic fissures: fibrosis at base and sentinel pile formation
• Painful defecation due to sphincter spasm and exposed nerve endings
• Bleeding due to disruption of small submucosal vessels