Anal Fissure



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 (>4 to 8 weeks in duration) and may be associated with the presence of hypertrophic papilla and sentinel pile (skin tag)


  • Affects all ages; common in infants 6 to 24 months; uncommon 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), as patients often treat with home remedies and do not seek medical care. However, one cohort study found the average lifetime risk in the United States to be 7.8%, equal to that of appendectomy (2).


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

None known

Risk Factors

  • Constipation (25% of patients)
  • Diarrhea (6% of patients)
  • Passage of hard or large-caliber stool
  • Low fiber diet
  • 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 (IBD) (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 (IBS); other/multiple locations: Crohn disease, tuberculosis, leukemia, and HIV

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