Anal Fissure

Anal fissure is usually caused by constipation and straining, resulting in a tear of the skin lining the (lower) anal canal. It is an extremely painful condition and is usually encountered in young and middle-aged adults.

The anal canal is surrounded by two sphincter muscles for continence. The internal muscle is an automatic muscle which should spontaneously relax when there is bowel motion in the rectum, the external muscle then being voluntarily contracted to control passage until it is convenient to use the toilet. When the skin overlying the internal muscle is torn, the muscle fails to relax, evacuation thus occurring against an incompletely relaxed (internal) sphincter. This exacerbates and perpetuates the spasm and thus the pain, creating vicious cycles of tearing and spasm and also tearing and attempting to heal. When the scar tissue builds up at the edges and apex of the fissure, there is less likelihood of successful conservative attempts at healing and the more likely surgical intervention becomes.

Conservative treatment includes warm baths, stool softeners such psyllium seed preparations and simple pain relief. “Rectogesic” (0.2% glyceryl trinitrate cream) will heal some 40% of the fissures by improving the local blood supply which helps to relax the anal sphincter muscles and allows the fissure to heal. Important research and development of this cream has occurred in Australia. Unfortunately compliance in using the cream is low because of the side effect of headache in as many as 70% of users. More recently, research has identified many other agents which appear to have the same efficacy without the headaches and some will soon be available.

Another agent that is currently being assessed botulinum toxin (“Botox”), the same substance used to regain a youthful facial appearance! Botulinum toxin is injected into the anal muscles to produce a temporary degree of muscle paralysis in the vicinity of the fissure, theoretically allowing effective healing. The success rate is however variable, ranging from 40-80%in various reports.

Operation is generally recommended after failure of conservative treatment.

Lateral sphincterotomy is the operation of choice with high success rates of 96-100% and very good patient satisfaction. Recurrence rates are as low as 1%. Although it carries a theoretical risk of incontinence, limiting the tiny incision to the height of the fissure has essentially eliminated this problem. This operation takes about 10 minutes in experienced hands and is carried out as a day procedure under intravenous sedation with the addition of local anaesthesia whilst asleep for maximal post-operative benefit.