MRI OF FISTULA-IN-ANO - A COMPARISON OF ENDOANAL COIL WITH EXTERNAL PHASED-ARRAY COIL TECHNIQUES

Purpose: The objective of our study was to compare MRI of fistulas-in- ano using an endoanal coil with that using a pelvic phased array coil and to assess the value of a combined approach by correlating the find ings with those at surgery. Method: Twenty consecutive patients with c linical suspicion of perianal sepsis were studied using an endoanal co il immediately followed by a phased array coil. T1 weighted and STIR i mages in transverse and coronal planes were made with each coil and an alysed by noting the presence and site of a collection and primary tra ck, the position of any internal opening, and subcutaneous or supralev ator extension. Operative findings were similarly recorded. Results: O f 20 patients with suspected fistulas, 8 had simple fistulas, 8 had co mplex fistulas, and 4 had no current evidence of infection. The concor dance between MR and surgery for identifying the presence and site of the collection, the primary track, and the internal opening in both si mple and complex cases was superior using the endoanal coil as compare d with the phased array. Both coils together reflected the findings of the endoanal coil used alone. However, for supralevator/subcutaneous extension, concordance was superior using the phased array compared wi th the endoanal coil, and a combined approach reflected the values of the phased array coil used alone. Conclusion: Endoanal MRT is highly s ensitive in the delineation of fistulas-in-ano. In combination with ph ased array techniques, it provides valuable preoperative assessment in both simple and complex cases.