High-resolution magnetic resonance imaging of the anorectal region without an endocoil.

Department of Radiology, University Hospital of Maastricht, Maastricht, Post Office Box 5800, 6202 AZ Maastricht, The Netherlands.

BACKGROUND: To evaluate the feasibility of a high-resolution magnetic resonance imaging (MRI) technique in detailed imaging of the anal sphincter and lower pelvic region without the use of an endoluminal coil. METHODS: MRIs with an external phased array coil (T1- and T2-weighted turbo spin echo) were performed in 22 volunteers and 12 patients with an anal fistula, an anal sphincter defect, or a rectal tumor. The normal scans were evaluated by three independent observers. The scans of the patients were compared with surgical and/or histologic findings. RESULTS: The anal sphincter was visualized with detail. In the anal canal, hemorrhoidal tissue and the submucosae ani muscle could be seen. The MRI technique also allowed detailed imaging of anatomical structures above the pelvic floor. The MR findings in the 12 patients showed exact correlation with surgery and/or histology. CONCLUSIONS: High-resolution MRI of the anorectal region without an endoluminal coil is feasible. The MR technique with an external phased array coil allows detailed imaging of the anal sphincter at rest, the rectum, and the surrounding pelvic structures with one single investigation. The results are promising and suggest useful applications in the management of anorectal diseases.