Transperineal ultrasound in the detection of perianal and rectovaginal fistulae in Crohn's disease

OBJECTIVES: Perianal and rectovaginal fistulae are common complications in Crohn's disease. Magnetic resonance imaging (MRI) and endoanal ultrasound are used for imaging perianal fistulae and abscesses, but both methods require expensive equipment and experienced investigators. Transperineal ultrasound may represent another method of detecting perianal complications in Crohn's disease. We investigated Crohn's disease perianal and rectovaginal fistulae using transperineal ultrasound and compared the findings with results of endoanal ultrasound as reference standard. METHODS: A total of 46 patients with Crohn's disease and perianal and/or rectovaginal or anovulvar fistulae underwent, transperineal and endoanal ultrasound, on the same day. Transperineal ultrasound was performed using regular convex and high-resolution linear probes. Endoanal ultrasound was performed using an ultrasound system with a 7 MHz rotating endoanal probe. Fistulae were classified according to Parks' classification in intrasphincteric, transsphincteric, suprasphincteric, and extrasphincteric. Rectovaginal or anovulvar fistulae were described separately. Presence of abscesses was also reported. RESULTS: Fifty-two fistulae (3 intra-sphincteric, 28 transsphincteric, 8 suprasphincteric, 2 extrasphincteric, 9 rectovaginal, and 2 anovulvar) were detected by transperineal ultrasound. Endoanal ultrasound confirmed the correct classification of 45 fistulae (predictive positive value: 86.5%). Of the 53 fistulae detected by endoanal ultrasound, 45 were correctly classified by transperineal ultrasound (sensitivity 84.9%). Transperineal ultrasound showed 10 perianal abscesses: 2 horseshoe, 4 deep, and 4 superficial. Endoanal ultrasound confirmed all horseshoe, 3 deep, and 2 superficial abscesses and did not find further abscesses. CONCLUSIONS: Transperineal ultrasound is a simple, painless, real-time method to detect and classify perianal and rectovaginal fistulae and/or abscesses in Crohn's disease.