Comparative study of percutaneous (perianal) instillation of aqueous jelly & percutaneous (perianal) gadolinium instillation in MR fistulography with its surgical correlation

Abstract

Background: Perianal fistula is an abnormal tract connecting the anal canal and the perianal skin. Precise delineation of the tracts is necessary before surgery to know the anatomical details in order to prevent recurrences and incontinence. We studied the efficacy of percutaneous (perianal) instillation of aqueous jelly versus percutaneous (perianal) gadolinium instillation on magnetic resonance (MR) fistulography and compared to intra-operative findings. Materials and Methods: All patients with suspected peri-anal fistula showing external opening and active perianal discharge, who were sent for MR fistulography. MR fistulography with aqueous jelly instillation of perianal external opening was done on day 1, MR fistulogram with percutaneous (perianal) instillation of gadolinium contrast was performed next day which were correlated surgically. Results: A total of 30 patients underwent MR fistulogram with both modalities, of which, 28 of them underwent surgery. Out of the 28 patients with intra-operative primary tract, all 28 were identified to have the primary tract. Secondary tract identification by aqueous jelly instillation showed sensitivity, specificity, PPV, NPV, and accuracy of 55.5%, 100%, 100%, 82.6%, and 85.7% respectively. Secondary tract identification by gadolinium instillation showed sensitivity, specificity, PPV, NPV, and accuracy of  77.7%, 100%, 100%, 90.4%, and 92.8% respectively.