Comparative study of non-contrast and post-contrast MR fistulogram in the evaluation of fistula in Ano
Background: Fistula in ano is a common inflammatory condition with significant morbidity. To evaluate the disease before planning any treatment, MRI has become a cornerstone involving both non-contrast and post contrast imaging as a routine protocol.
Aim: The current study has aims to evaluate the diagnostic efficacy of non-contrast MRI over post contrast MRI in the evaluation of perianal fistulas.
Methods: 122 patients of perianal fistulas were included in this observational study who had undergone contrast-enhanced MRI prior to surgery. Non-contrast data sets were compared with the post-contrast data sets.
Results: The sensitivity of delineating Grade 1 perianal fistulas, as per St James university classification, on non-contrast imaging was found to be 81.03 %. The sensitivity was found to be 75%, 88.66% and 91.30% for Grade 2, 3, and 4 fistulas respectively, which increases to 100% in Grade 5 perianal fistulas.
Conclusion: On comparison of the non-contrast data set with the post-contrast images, the findings were found comparable. In higher grades of perianal fistulas, the sensitivity of evaluating the disease on non-contrast images is at par with post-contrast imaging. Contrast study, being more expensive, time-consuming and risky modality should be avoided as a routine and could be considered in low-grade perianal fistulas on case to case basis.
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