anal fissure

Introduction

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

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

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