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; 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) 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.
- 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 (Crohn disease)
- Infection (chlamydia, syphilis, herpes, tuberculosis)
All measures to prevent constipation; avoid straining and prolonged sitting on toilet.
Commonly Associated Conditions
Posterior midline location: constipation, irritable bowel syndrome; other/multiple locations: Crohn disease, tuberculosis, leukemia, and HIV
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