An anal fissure is a disruption of the skin at the distal anal canal.
Most fissures are seen by separating the buttocks with opposing traction of the thumbs.
Majority of fissures are located in the posterior midline of the anus.
Acute fissures are simple splits or cracks in the anoderm while chronic fissures may show secondary changes eg sentinel tag, hypertrophied anal papilla, rolled edges, fibrosis of the edges or deep ulceration with exposure of the underlying internal sphincter muscle.

Principles of Therapy

Diet modification and medical therapy constitute the initial treatment for anal fissures

  • Treatment aims to relieve constipation, because softer bowel movements are less painful for the patient to pass
  • Acute fissures respond better to medical therapy better than chronic fissures
  • Second-line therapy may be used for patients wanting to avoid surgical therapy
  • Therapy is aimed at reversibly decreasing resting anal pressure with the goal of allowing the fissure to heal without permanent sphincter damage


Agents to Relieve Constipation

  • Fiber supplementation given within a high-fiber diet increases stool bulk
  • Stool softeners eg Docusate sodium and Docusate calcium diminish bleeding and pain
  • Laxatives help maintain regular bowel movement
  • Please see comprehensive list of available agents for constipation in the latest MIMS

Topical Sphincter Relaxants


  • Topical glyceryl trinitrate (GTN) has been shown to significantly decrease pain during treatment
  • Action: Reduce resting anal pressure and improve blood flow to the anoderm
  • Headache is the most common side effect
  • The need for repeated applications may result in poor compliance and subsequent therapy failure for many patients
  • GTN may potentiate the effect of Botulinum toxin in patients being treated for refractory fissures
  • Other agents that have been studied are topical Isosorbide dinitrate ointment and spray
  • Patients unresponsive to topical nitrates should be referred for Botulinum toxin injection or surgery

Calcium Antagonists

  • Topical Ca antagonists are associated with a higher rate of fissure healing and a lower incidence of side effects than oral forms
  • Several studies show that topical Ca antagonists appear to be as effective as treatment with topical GTN, with fewer side effects
  • Action: Decrease resting anal pressure and anal slow/ultra-slow wave activity

Botulinum Toxin Injections

  • Action: Inhibit acetylcholine release from presynaptic nerve terminals which achieves a chemical sphincterotomy
    • At higher doses, may also transiently decrease mean squeeze pressure
  • Effect lasts about 2-3 months until nerve endings regenerate, during which time the fissure may heal
    • Healing takes longer than after surgical sphincterotomy, but return to full activity occurs sooner
  • Most common side effect is transient incontinence to flatus and stool incontinence occurs less commonly
  • High cost of treatment is a disadvantage
  • Fissure recurrence after 3 months suggests that patient may benefit from surgical sphincterotomy
  • There is inadequate consensus on dosage, precise site of administration, number of injection needed, or efficacy

Other Pharmacological Agents

  • Other agents being used or studied for anal fissure include the following:
    • Muscarinic agonists eg topical Bethanechol, adrenergic antagonists eg Indoramin and beta2-agonists eg Salbutamol
      • Topical Bethanechol is effective in healing anal fissure without significant side effects
    • Lidocaine and Hydrocortisone

Non-Pharmacological Therapy

Other Measures

  • Sitz baths relax painful internal sphincter muscle spasm
  • Topical anesthetics may be used to increase patient comfort and they cause no harm
  • Mineral oil may be used short-term to minimize stretching of the anal mucosa by easing stool passage
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