The Diagnostic Concordance of Endoanal Ultrasonography and Endoanal MRI in Cases of Anorectal Fistula

ABSTRACT

PURPOSE: To evaluate the preoperative diagnostic concordance of morphologic classification of anorectal fistula by endoanal ultrasonography (EUSG) and endoanal magnetic resonance imaging (EMRI). MATERIALS AND METHODS: Between January 1998 and March 1999, 17 patients with anorectal fistula underwent endoanal ultrasonography and magnetic resonance imaging for preoperative assessment. The types of fistula and abscess formation were evaluated, and the findings compared with those obtained during surgery. RESULT: The overall accordance of anorectal fistula was 76% (13 of 17 cases) on ultrasonography and 94% (16 of 17 cases) on magnetic resonance imaging. According to the findings of EUSG, the accordance of each type of anorectal fistula was as follows transphineteric, 92% (11 of 12 cases); suprasphinteric, 33% (1 of 3); and extrasphincteric, 50% (1 of 2), while for EMRI, the respective figures were 100% (12 of 12 cases), 67% (2 of 3), and 100% (2 of 2). An analysis of reproducibility using kappa value showed that overall concordance between endoanal ultrasonography and surgery(K=0.820) as well as between endoanal MRI and surgery (K=0.866), was very close. CONCLUSION: For the evaluation of anorectal fistula, preoperative endoanal magnetic resonance imaging was more accurate and informative than endoanal ultrasonography.