Fissure is common, lying on the inside of the distal anal canal, usually posteriorly, but it is easily missed clinically unless traction is exerted on the rim of the anal canal. Local trauma by constipated stools leads to a tear; spasm and the resulting poor perfusion lead to an ischaemic ulcer which fails to heal.1

Non-operative treatments such as laxatives and local anaesthetics try to break the pain/constipation cycle. In failures, surgical sphincterotomy reduces resting anal pressure, improves local blood flow and successfully heals the fissure, but at the price of (usually minor) incontinence in a few.  Resting anal pressure can also be reduced either by local application of a nitric oxide donor such as glyceryl trinitrate (GTN) or by injection of botulinum toxin A. Maria et al report a small randomised …