Magnetic resonance imaging of fistula-in-ano.

PURPOSE Successful management of anal fistulas depends upon accurate assessment of the primary tract and any secondary extensions. Preoperative imaging has, to date, been disappointing. METHODS A prospective study of 35 patients with a clinical diagnosis of fistula-in-ano was performed comparing magnetic resonance imaging with the independently documented operative findings. Magnetic resonance imaging was also compared with anal endosonography in 20 patients. RESULTS Magnetic resonance imaging is accurate and demonstrates pathology missed at surgery by experienced coloproctologists. Magnetic resonance imaging is superior to anal endosonography. CONCLUSIONS Magnetic resonance imaging is advocated as the method of choice when imaging is required for anal fistulas.