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Internal Medicine

Anal fissure

Tear in the anoderm distal to the dentate line.

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Classic anal fissure | Courtesy of W. Brian Sweeney, MD
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Diagram of anal fissure | Schlichtemeier, S., & Engel, A. (2016). Anal fissure. Australian Prescriber, 39(1), 14–17. https://doi.org/10.18773/austprescr.2016.007

Aetiology

  • Low-fibre diet
  • Constipation
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Incidence of anal fissure (cases per 1000 persons per year) by sex and age group. | Mapel, D. W., Schum, M., & Von Worley, A. (2014). The epidemiology and treatment of anal fissures in a population-based cohort. BMC Gastroenterology, 14, 129. https://doi.org/10.1186/1471-230X-14-129

Pathophysiology

Acute injury

Local pain & spasm of the internal anal sphincter↑ resting anal sphincter pressure

↓ blood flow

Ischaemia and poor healing

Unless this cycle is broken the fissure will persist.

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Pathophysiology of anal fissure | Schlichtemeier, S., & Engel, A. (2016). Anal fissure. Australian Prescriber, 39(1), 14–17. https://doi.org/10.18773/austprescr.2016.007

Site:

  • Posteriorly midline fissure (M/C, 90% cases; d/t poor perfusion)
  • Anterior fissure (10% cases; usually younger, mostly female, patients often with injury to or dysfunction of the external anal sphincter)
  • Lateral/multiple fissures (<1% cases)

Clinical features

  • Anal pain, spasm, and/or bleeding with defecation

Complications:

  • Bleeding
  • Pain
  • Infection
  • Incontinence
  • Fistula formation (M/serious)

Diagnosis

Differential diagnosis:

Other causes of severe anal pain
  • Thrombosed external haemorrhoids
  • Anal fissure
  • Acute herpetic ulceration or other STD
  • Crohn’s ulceration & inflammation
  • Anal, rectal or pelvic cancer
  • Lymphoma/leukaemia

Management

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Recommended treatment algorithm. GTN: Glyceryl trinitrate | Poh, A., Tan, K.-Y., & Seow-Choen, F. (2010). Innovations in chronic anal fissure treatment: A systematic review. World Journal of Gastrointestinal Surgery, 2(7), 231–241. https://doi.org/10.4240/wjgs.v2.i7.231

Surgical management:

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Open lateral sphincterotomy | Courtesy of W. Brian Sweeney, MD

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