Accuracy of Goodsall’s Rule in Perianal Fistulas – Correlation with Mr Fistulogram

Abstract

Introduction: Perianal fistula is one of the common gastrointestinal pathology with significant morbidity.
Goodsall’s rule states that the posterior perianal fistulas have the fistulous tract that opens into the anal canal
in the midline posteriorly, sometimes taking a curvilinear course and anterior perianal fistulas will have a
radial fistulous tract.
Objectives: To assess the accuracy of Goodsall’s rule in perianal fistulas on comparison with Magnetic
Resonance (MR) fistulogram findings.
Materials and Methods: A total of 45 cases with perianal fistula underwent pre-operative MR Fistulogram
assessment. Fistulas were divided into anterior and posterior fistulas based on MR Fistulogram findings.
Accuracy of Goodsall’s rule in all the perianal fistulas visualised on MRI was assessed.
Results: Out of 45 patients, 10(22.2%) patients had anterior fistulas and rest of 35(77.8%) patients had
posterior fistulas. Goodsall’s rule was valid in 28(62.2%) patients. Seventeen (37.8%) patients did not follow
Goodsall’s rule. Goodsall’s rule was found to be more accurate in anterior fistulas than posterior fistulas.
Conclusion: MR Fistulogram has high accuracy of detecting perianal fistulas. Goodsall’s rule may not be
valid in all the cases of perianal fistulas. Goodsall’s rule is more applicable in anterior fistulas. Posterior
fistulas do not strictly adhere to Goodsall’s rule with many of them showing linear tracts. This information
is useful for pre-operative planning of fistula treatment.