Objective: MRI has been reported to be valuable in the investigation of patients with fistula in ano. The aim of this study was to evaluate the results of preoperative magnetic resonance imaging (MRI) in such patients using a surface coil and to compare it with surgical findings.
Patients and methods: In a prospective study, 28 patients (19 males, nine females, median age 39 years) with perianal fistula underwent preoperative MRI. Parks classification as well as the identification of an internal opening into the anal canal and/or rectum were compared with the surgical findings.
Results: Classification during surgery revealed five extrasphincteric, eight transsphincteric, seven suprasphincteric and eight intersphincteric fistulas. All patients with intersphincteric, suprasphincteric and transsphincteric fistulas were correctly classified by MRI. The comparison of MRI and surgical results revealed a concordance in 27 of 28 (96%) patients in terms of classification (κ 0.95, P < 0.01) and in 21 (75%) patients regarding the identification of the internal opening (sensitivity 63%, specificity 92%).
Conclusion: Our results indicate that MRI of perianal fistulas with the use of extra-anal surface coils can accurately assess the surgical anatomy. It is a rapid, well-tolerated technique which might play an important role in the management of perianal fistula.