Three-dimensional endoanal ultrasound for the locational diagnosis of anal fistula: a preliminary application study BEI Shao-sheng，DING Ke, WANG Jian-xin, et al．Department of Anorectal Surgy，the Second Hospital of Shandong University，Jinan 250033，China Corresponding author：DING Ke，E-mail：dingke@163.com Abstract Objective To evaluate the effectiveness and applied value of three-dimensional (3D)-Endoanal ultrasound combined with hydrogen peroxide angiography for the locational diagnosis of anal fistula. Methods 3D-endoanal ultrasound examination was performed in 17 patients with clinically suspected anal fistulas between November 2008 and January 2009 at the Second Hospital of Shandong University and results were compared with surgical findings. Results Seventeen patients were confirmed by 3D-endoanal ultrasound examination. Nine patients had simple fistulas. Eight patients had complex fistulas. At the same time 7 patients had low located fistulas, and 10 patients had high located fistulas including 8 patients with trsphincter fistulas, 1 patient with inter sphincter fistula and 1 patient with extra-sphincter fistula. All patients were confirmed by operation. But on surgery’s professional examination 1 case with high located fistulas was remisdiagnosed as low located fistulas.3D-Endoanal ultrasound had a accuracy of 90.9%. The 3D shape and track of fistula could be well shown the site of anal fistula and its relationship with the phincter complex and the levator animuscle. Conclusion 3D-Endoanal ultrasound examination combined with fistulography is a very effective and reliable method for the locational diagnosis of anal fistula.