Goodsall’s Rule Revisited: An MRI-Based Assessment of its Accuracy in Perianal Fistulas

Aim: The aim of this study is to evaluate the accuracy of Goodsall's rule in predicting the internal orifice of perianal fistulas based on magnetic resonance imaging (MRI) findings and to assess its relevance in contemporary imaging and surgical planning. Method:In the retrospective analysis of 1,473 consecutive MRI scans performed for perianal fistulas, a total of 305 patients (men/women: 214/91) with a single fistula were included in the study.Fistulas were classified as anterior or posterior based on the external orifice position relative to the transverse anal line.Results: Posteriorly located fistulas were more common (61.3% vs. 38.7%).The accuracy of Goodsall's rule was higher in anterior fistulas (64.4%) than in posterior fistulas (39.6%; p<0.001).There was no statistically significant difference in adherence to the rule between genders (p=0.416),different types of fistulas according to the Parks classification (p=0.588), or presence of abscess (p=0.464).Comorbidities significantly affected the accuracy of the rule (p=0.017).In the Bonferroni-adjusted analysis, no significant difference in adherence was found between the cryptoglandular and Crohn's disease groups (p>0.05).Among the 11 patients with malignancy, only 1 (9.1%) adhered to the rule, indicating reduced accuracy. Conclusion:Goodsall's rule is more accurate for anterior fistulas; however, it does not apply to all perianal fistula cases, with greater exceptions observed in posterior fistulas.MRI should be considered for all perianal fistulas when possible to improve diagnosis and outcomes.