What is the Goodsall rule
The Goodsall rule helps predict the location of the internal opening of an anal fistula based on the site of its external opening. Accurately determining the criminal crypt of fistula origin on the dentate line is important at the time of surgical treatment, generally fistulotomy. If the anus is divided into imaginary anterior and posterior halves in the coronal plane, posterior fistulas tend to curve into the posterior midline. Anterior fistulas shorter than 3 cm tend to proceed radially to the dentate line, whereas anterior fistulas longer than 3 cm may track back to the posterior midline.