Three-dimensional pelvic ultrasound is a practical tool for the assessment of anal fistula.

Objective: This study aims to investigate the diagnostic value of three-dimensional pelvic ultrasound in the preoperative assessment of anal fistula compared with findings of MRI and surgery.

Methods: A total of 67 patients (62 males) with suspected anal fistula were analyzed retrospectively. Preoperative three-dimensional pelvic ultrasound and magnetic resonance imaging were performed in all patients. The number of internal openings and the type of fistula were recorded. The accuracy of three-dimensional pelvic ultrasound was determined by comparing these parameters with surgical outcomes.

Results: At surgery, 5 (6%) were extrasphincteric, 10 (12%) were suprasphincteric, 11 (14%) were intersphincteric, and 55 (68%) were transsphincteric. There was no significant difference in the accuracy of pelvic 3D US and MRI, based on internal openings (97.92%, 94.79%), anal fistulas (97.01%, 94.03%), and those under Parks classification (97.53%, 93.83%).

Conclusion: Three-dimensional pelvic ultrasound is a reproducible and accurate method for determining the type of fistula and detecting internal openings and anal fistulas.