High-resolution MRI for primary anal fistulas

Objective: To evaluate the accuracy and clinical value of preoperative high-resolution magnetic resonance (MR) imaging with a phased-array coil for the detection of anal fistulas. Methods: A total of 20 patients with surgically proved anal fistulas underwent preoperative MR imaging with phased-array coil at 1.5 T MR unit. The imaging protocol included high-resolution T₂-weighted turbo spin echo sequence acquisition at axial, sagittal and coronal planes and axial T₂-weighted sequence with fat suppression. Results: Twenty patients were found to have 27 fistulas, 24 internal openings, 28 external openings, and 10 perianal abcesses. The sensitivity and specificity for detecting primary fistula tracks, abscesses and internal openings were 92.6% (25/27) and 92.3% (12/13), 100.0% (10/10) and 96.3% (26/27), 91.7% (22/24) and 85.7% (12/14), respectively. Conclusion: High-resolution MR imaging is a very accurate preoperative technique for evaluating the classification of fistula-in-ano, the course of primary tracks and the presence of abscesses, thus providing important information for proper surgical treatment.