Predictive accuracy of Goodsall’s rule for fistula-in-ano

Successful treatment of fistula-in-ano is sometimes challenging due to difficulty in recognising the internal opening and the course of the fistula tract. Although Goodsall’s rule was accepted in the past, as a method to determine the course of the fistula, recent data have shown conflicting results.

To study the predictive accuracy of Goodsall’s rule.

A sample of 212 patients with simple fistulae were studied. Hydrogen peroxide was injected through the external opening and the appearance of air bubbles in the anal canal indicated the location of the internal opening. The morphological parameters including the site and number of internal and external opening/s and the course of the tract were recorded.

The median age of the participants was 39 (range, 18-78) years. The majority (n=167, 78.8%) were males. Of the study group, 63 (29.7%) had inter-sphincteric fistulae, 114 (53.8%) transphincteric fistulae and 35 (16.5%) superficial fistulae. The overall predictive accuracy of Goodsall’s rule in our patients was 78.3%. Predictive accuracy was significantly associated with type of fistulae with high predictive accuracy seen in superficial fistulae (97.1%) and inter-sphincteric fistulae (84.1%) compared to transphincteric fistulae (69.3%) (p=0.001). Predictive accuracy was significantly higher in those with an external opening in the midline (98.2%), (p<0.001).

Although Goodsall’s rule was not accurate in 22% of all fistulae, it can be used as a guide in locating the path of the tract and the internal opening in simple fistulae.