anal fissure

see also:

• perianal abscess
• perirectal abscess
• haemorrhoids
• ano-rectal pain
• anal fistula / fistula-in-ano
• proctitis
• PR_exam
• Aust Prescr. 2016 Anal fissure

• anal fissure is a common acutely painful condition of the anus
• it is usually due to “microtrauma” but may be secondary to other illnesses
• most are benign and resolve over a week to 6 weeks but some may become chronic and require surgical intervention
• late recurrences occur in 50%

• “microtrauma” due to:
  • passage of hard stools
  • diarrhoea
  • childbirth
  • repetitive injury or penetration

• PH anal surgical procedures
• inflammatory bowel disease (IBD)
• granumolatous diseases (sarcoid, tuberculosis (TB))
• infections (HIV / AIDS, syphilis)
• neoplasia / cancer / tumours

• histology does not usually show evidence of an inflammatory process
• 90% are located on the posterior midline and are generally primary fissures
  • perhaps due to the poorer perfusion
• 10% are located on the anterior midline and may have a different pathophysiology and tend to occur more in younger patients especially women
• < 1% are lateral or multiple and these tend to be due to secondary causes

• microtrauma leads to a tear
  • ⇒ pain
    • ⇒ internal sphincter spasm
      • ⇒ high resting anal pressure
        • ⇒ reduced anodermal perfusion
          • ⇒ local ischaemia
            • ⇒ poor healing
              • ⇒ chronicity

• usually sudden onset of anal pain after passing stool
• most are able to be seen on PR exam:
  • an acute anal fissure appears as a fresh laceration
  • a chronic anal fissure has raised edges exposing the internal anal sphincter muscle fibres underneath
• a digital PR exam is exquisitely tender especially at the location of the fissure which is usually at 12 o'clock in lithotomy position
  • a digital PR exam is not usually needed in cases where it is evident by looking
• a secondary sentinel pile (external skin tag) will usually form at the top of the fissure
• increased anal tone due to pain

• exclude other causes of ano-rectal pain by examination
• conservative Mx with:
  • stool softeners
  • topical anaesthetics prn
  • encourage fluid intake
  • warm sitz baths
  • simple analgesics
  • topical glyceryl trinitrate is better than placebo in healing anal fissures (healing rates 49% vs 36%) but causes headaches and lightheadedness causing many to cease using it
  • topical 2% diltiazem cream bd has superior healing rates to oral diltiazem (65% vs 38%) and whilst they commonly cause headaches, these are not as bad as those from GTN
• consider EUA if either:
  • fissure cannot be seen
  • diagnosis is unclear
  • there is significant bright red bleeding in a patient with an increased risk for colorectal cancer
  • there are features suggesting a secondary anal fissure
• consider surgical referral if it has become chronic as may benefit from either:
  • pneumatic balloon dilation
    • healing rates of 83%, approaching those of lateral internal sphincterotomy, but with a lower incidence of long-term incontinence
  • lateral internal sphincterotomy
    • usually done at 6-8 weeks if not healed
    • superior to the four-finger anal stretch
  • botox injection
    • similar efficacy to topical GTN or diltiazem
    • may cause temporary incontinence of flatus (in up to 18%) and stool (in up to 5%)
  • four-finger anal dilatation no longer used