Anal Fissure

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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


  • 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%)

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.
  • Lateral fissure: Rule out infectious disease.
  • Atypical fissure: Rule out Crohn disease.

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.

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

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