Anal Fissure

An anal fissure is a linear tear in the anoderm, usually extending from the anal verge toward the dentate line.

Most primary fissures occur in the posterior midline. Anterior midline fissures are less common.

Acute fissures usually follow trauma from hard stool, constipation or diarrhoea.

A lateral, multiple or atypical fissure should raise concern for Crohn disease, tuberculosis, HIV associated disease, syphilis, malignancy or another secondary cause.

The characteristic symptom is severe sharp pain during defaecation followed by burning or spasm that can persist for minutes to hours.

A small amount of bright red blood may appear on stool or tissue.

Inspection usually reveals the fissure without requiring painful instrumentation.

Diagnosis is clinical.

Avoid forceful digital rectal examination or anoscopy when the fissure is acutely painful and the diagnosis is externally obvious.

Investigate atypical fissures rather than repeatedly treating them as primary disease.

Most acute fissures heal with reduction of stool trauma.

Use:

• Fibre approximately 20 to 30 g daily
• Adequate oral fluid
• Warm sitz baths
• Avoidance of straining

If constipation is present:

Polyethylene glycol 17 g orally once daily, titrated according to stool consistency.

Local anaesthesia can provide short term pain relief:

Lidocaine 2% topical gel applied sparingly before defaecation as required.

Avoid prolonged dependence on topical anaesthetic preparations because they do not correct sphincter hypertonicity or the underlying injury.

Most acute fissures do not require surgery.