Anal Fissure

Tear or ulcer in the lining of the anal canal, immediately within the anal margin.

Classification

  • Acute (<6 weeks) vs Chronic (>6 weeks)
  • Primary (no underlying cause) vs Secondary (underlying cause)

Aetiology and Pathophysiology

  • Primary
    • Thought to be due to increased anal tone after an initial fissure injury caused by the passage of a hard stool.  The increased tone impairs healing by impairing blood flow to the area, worsening ischaemia.  The result is painful passage of stools- the pain of which can last several hours.
  • Secondary
    • NB Not associated with increased tone or ischaemia
    • Causes include
      • Constipation
      • IBD
      • Malignancy of the anorectal canal

Presentation

  • Often classic history of severe pain when passing stools, and it may be that the patient doesn’t like going (this only worsens the cycle, by increasing anal tone further)
  • Bleeding (usually fresh blood) may be present upon defaecation
  • Some may have a history of constipation
  • On examination
    • Most fissures occur in the posterior midline (12 o’clock position) with the remainder commonly in the anterior midline (6 o’clock position)
    • If a tear can be seen clearly (well-defined), this is more likely to be acute.  Chronic fissures commonly appear a bit scarred, wider or deeper with muscle fibres visible or there may be a skin tag overlying the area.
    • NB PR examination is often very painful and not suitable.

Anal fissures are often a clinical diagnosis so investigation are no required.  If there is suspicion over the cause or concerns about blood loss, then further investigations may be appropriate.

Management

  • Ensure soft, easily passed stool
    • Laxatives (lactulose- osmotic laxatives) are recommended in children
    • Bulk-forming laxatives e.g. ispaghula husk, are recommended for adults
    • Similarly, increasing dietary fibre intake should be advised.
      • Fruit/veg/grains etc
      • Adequate fluids too
      • Aim between 18-30g of fibre
  • Pain relief- paracetamol and/or ibuprofen
  • Consider GTN ointment or topical diltiazem in those who cannot be managed with other conservative measures (particularly in patients with large fissures at initial presentation)
  • Surgery (sphincter dilatation or, more commonly, lateral internal sphincterotomy) may be offered to patients with chronic or unresolved symptoms/signs after 6-8 weeks (if asymptomatic 12-16 weeks)

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