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 or chronic (>8 weeks) in duration or with the presence of hypertrophic papilla and sentinel pile (skin tag).

Epidemiology

• Affects all ages. Common in infants aged 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) coupled with decreased perfusion of the posterior canal 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

Posterior midline location: Constipation, irritable bowel syndrome; other locations: Crohn disease, tuberculosis, leukemia, and HIV