Comparison of conventional and limited selected sequences of MRI in evaluation of Perianal Fistulas

Abstract

Background: The purpose of the study was to establish a protocol for application of limited selected sequences in MRI and to establish pitfalls and negative predictive factors in MR imaging of perianal fistulas with limited sequences.Materials and methods: Total 50 patients who were clinically diagnosed with perianal fistula diagnosis were included in this study. MR findings were recorded as per St. James’s University Hospital classification of perianal fistulas. We have correlated findings of conventional MRI sequences with surgery followed by comparison of scores of conventional and limited sequences based on MRI findings. In our scoring system, each MRI finding was given a single score.Results: Of the total 50 patients, 42 patients in conventional sequences confirmed as perianal fistula per-operatively. Sensitivity, specificity, PPV, NPV and accuracy of conventional sequences in correlation to surgery was found to be 95%, 67%, 95%, 67% and 92% respectively. Limited sequences were compared with conventional sequences on the basis of scoring system. Total scores for internal opening and primary tract were decreasing whereas there was no change in total score for external opening, secondary tracts and abscesses.Conclusion: Conventional sequences can detect relatively more number of primary tracts, internal openings and secondary tracts in comparison to the limited sequences, so conventional sequences should be preferred over limited sequences for the diagnosis of perianal fistulas except in uncooperative patients where limited sequences consume less time than conventional sequences.