Goodsall’s rule can be used to clinically predict the course of an anorectal fistula tract. Imagine a line that bisects the anus in the coronal plane (transverse anal line). Any fistula that originates anterior to the line will course anteriorly in a direct route. Fistulae that originate posterior to the line will have a curved path. An exception to the rule are anterior fistulas lying more than 3 cm. from the anus, which may open in the anterior midline of the anal canal.