Background: Endosonography and magnetic resonance imaging (MRI) are promising methods for evaluating perineal and anorectal fistulas or abscesses. The aim of this study was to compare the results of anal endosonography (AES), MRI and surgical exploration in the assessment of anorectal fistula or abscess complicating Crohn's disease.
Methods: Twenty-two patients with Crohn's disease, seven men and 15 women of mean age 38 (range 17-67) years, were included in this prospective study. All patients underwent AES (linear probe 7 MHz), MRI and operative assessment.
Results: AES and MRI demonstrated 14 and nine abscesses respectively, whereas 11 abscesses were confirmed by surgical exploration in ten patients. The sensitivity of AES and MRI as means of evaluating anorectal abscesses was 100 and 55 per cent respectively. The agreement per patient was 86 per cent (19 of 22) for AES and 59 per cent (14 of 22) for MRI. AES and MRI demonstrated 26 and 14 fistulas respectively, whereas 27 fistulas were confirmed during surgical exploration in 16 patients. The sensitivity of AES and MRI was 89 and 48 per cent respectively. The level of agreement per patient was 82 per cent (18 of 22) for AES and 50 per cent (11 of 22) for MRI.
Conclusion: AES with a linear probe is more accurate than MRI in detecting anorectal abscesses complicating Crohn's disease, and much more accurate in the evaluation of complex fistulas.