A classification of fistula-in-ano.

A classification of anal fistulas is presented, which is the result of an analysis of 400 cases treated over the past 15 years, based on the pathogenesis of the disease and the normal muscular anatomy of the pelvic floor. Four main types were found but numerous variations of each occur, which are described. It is hoped that this will alert the surgeon to the various complex situations that he may encounter.