Another common condition in which there is an infected tract which connects deeply in the anal canal or rectum and superficially in the skin around the anus. It usually follows on from an anorectal abscess which bursts spontaneously or had been treated with inadequate surgery. There is a continuous discharge of pus/faeces from the skin opening around the anal verge. There are various types of anal fistula and the internal opening can be low or high. In complex situations, an MRI scan is necessary to get an accurate picture of the extent of the problem. Surgical intervention is always necessary, including sometimes staged operations and use of seton along with a prolonged period of regular dressing for a permanent cure.