Challenging the predictive accuracy of Goodsall's rule for anal fistulas.

To examine the predictive accuracy of Goodsall's rule, the records of 216 patients (155 men and 61 women) who underwent surgery for complete submuscular anal fistulas from 1982 to 1989 were retrospectively reviewed. In accordance with Goodsall's rule, 90 percent of 124 patients with an external opening posterior to the transverse anal line had anal fistulas tracking to the midline (87 percent men and 97 percent women). Only 49 percent of the 92 patients with an external opening anterior to the transverse anal line had anal fistulas that tracked in the radial fashion predicted by Goodsall (57 percent men and 31 percent women). Instead, 71 percent of these patients (62 percent men and 90 percent women) had anterior fistulas tracking to the midline. Overall, 81 percent (77 percent men and 93 percent women) of patients had complete submuscular anal fistulas that coursed to the midline (51 percent midline posterior and 30 percent midline anterior). In summary, Goodsall's rule is accurate only when applied to complete submuscular anal fistulas with posterior external anal openings. The rule is inaccurate in describing the course of complete submuscular anal fistulas with an anterior external opening. The men in this group had anal fistulas that defied Goodsall's rule in an unpredictable manner, whereas 90 percent of the women had fistulas tracking to a midline anterior origin.