Description

Anal fissure (fissure in ano): longitudinal tear in the lining of the anal canal distal to the dentate line, most commonly at the posterior midline; characterized by a knifelike tearing sensation on defecation, often associated with bright red blood per rectum. This common benign anorectal condition is often confused with hemorrhoids; may be acute (<8 weeks) or chronic (>8 weeks) in duration

Epidemiology

• Affects all ages. Common in infants 6 to 24 months; not common in older children, suspect abuse, or trauma; elderly less common due to lower resting pressure in the anal canal
• Sex: male = female; women more likely to get anterior midline fissures (25%) versus men (8%)

Incidence
Exact incidence is unknown (1). Patients often treat with home remedies and do not seek medical care.

• 80% of infants, usually self-limited
• 10–20% of adults, most of whom do not seek medical advice.

Etiology and Pathophysiology

High-resting pressure within the anal canal (usually as a result of constipation/straining) leads to ischemia of the anoderm, resulting in splitting of the anal mucosa during defecation and spasm of the exposed internal sphincter.

Genetics
None known

Risk Factors

• Constipation (25% of patients)
• Diarrhea (6% of patients)
• Passage of hard or large-caliber stool
• High-resting pressure of internal anal sphincter (prolonged sitting, obesity)
• Trauma (sexual activity or abuse, foreign body, childbirth, mountain biking)
• Prior anal surgery with scarring/stenosis
• Inflammatory bowel disease (Crohn disease)
• Infection (chlamydia, syphilis, herpes, tuberculosis)

General Prevention

All measures to prevent constipation; avoid straining and prolonged sitting on toilet.

Commonly Associated Conditions

Constipation, irritable bowel syndrome, Crohn disease, tuberculosis, leukemia, and HIV