Anal Fissure

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

An anal fissure is a linear tear or ulcer in the anoderm (lining of the anal canal) that causes pain and bleeding, usually during defecation.

Aetiology

Anal fissures can be classified into:

  • Primary fissures: occurs from trauma to the anal canal, commonly due to hard stools or straining.
  • Secondary fissures: happens with underlying conditions such as inflammatory bowel disease (IBD), sexually transmitted infections, or malignancy.

Pathophysiology

  • Trauma causes a tear in the anoderm, leading to pain and bleeding.
  • Increased resting anal sphincter tone reduces blood flow to the area, impairing healing.
  • Chronic fissures develop fibrosis, sentinel skin tags, and hypertrophied anal papillae.

Risk factors

  • Constipation and hard stools.
  • Chronic diarrhoea.
  • Pregnancy and childbirth.
  • Inflammatory bowel disease (e.g., Crohn’s disease).
  • Anal intercourse or trauma.
  • Post-surgical complications.

Signs and symptoms

Symptoms:

  • Severe, sharp pain during and after defecation.
  • Bright red blood on toilet paper or stool.
  • Pruritus ani (anal itching).
  • Fear of defecation due to pain.

Signs:

  • Visible tear at the anal verge (most commonly in the posterior midline).
  • Sentinel pile (skin tag) in chronic cases.
  • Excessive sphincter tone on digital rectal examination.

Investigations

  • Clinical diagnosis: history and examination.
  • Proctoscopy: To assess for secondary causes if indicated.
  • Colonoscopy or sigmoidoscopy: If red flag symptoms are present (e.g., weight loss, change in bowel habits, anaemia, or suspicion of malignancy).
  • Fit stool test (optional): to rule out other causes.

Management

1. Conservative Management:

  • Dietary changes: high-fibre diet and increased fluid intake to prevent constipation.
  • Stool softeners: e.g., lactulose or macrogol to ease defecation.
  • Sitz baths: warm water baths to relieve pain and improve blood flow.

2. Pharmacological Management:

  • Topical glyceryl trinitrate (GTN) 0.2% ointment: reduces anal sphincter spasm and improves healing.
  • Calcium channel blockers (topical diltiazem): can be used as an alternative to GTN.
  • Botulinum toxin (Botox) injection: considered in cases resistant to topical treatments.

3. Surgical Management:

  • Lateral internal sphincterotomy (LIS): gold standard for chronic fissures that fail conservative treatment.
  • Fissurectomy: removal of chronic fissures if needed.

Referral

  • Routine gastro referral: if symptoms persist despite medical treatment.
  • Urgent referral: if red flag symptoms suggest malignancy or inflammatory bowel disease.
GastroenterologymypanotesAnal Fissure