The value of magnetic resonance imaging geometric parameters in pre-assessing the surgical approaches of pelvic fracture urethral injury

Background: T o investigate the correlation between the magnetic resonance urethrography and the surgical approach and complexity for the patients with pelvic fracture urethral injury (PFUI) by combining the geometry with magnetic resonance imaging (MRI). Methods: Forty-three male patients with PFUI (part of the patients complicated with rectal injury) from January 2016 to December 2018 were analyzed in this retrospective research. All the patients underwent a delayed anastomotic urethroplasty and were divided into 2 groups according to the approaches (simple perineal approach or inferior pubectomy). For magnetic resonance urethrography, we measured and calculated the geometric parameters such as the gap distance between two urethral ends, the pubourethral vertical distance (PUVD), and the rectourethral median distance (RUMD). Results: Of the 43 patients, 16 underwent inferior pubectomy and 27 underwent simple perinea! approach. The numbers of patients with and without rectal injury history were 17 and 26, respectively. The operation time and intraoperative blood loss was significantly higher in the inferior pubectomy group. Multivariate logistic analysis revealed that gap distance and PUVD were independent factors of the surgical approaches. The accuracies were 83.7% and 67.4% respectively in the ROC curve analysis. In addition, the RUMD was significantly shorter in the patients with rectal injury history (1.4, 1.8 cm). Conclusions: Longer gap distance and shorter PUVD were the two independent factors of the inferior pubectomy approach. Furthermore, among the patients with rectal injury history, the tissue posterior to the urethra was often weaker and should be carefully handled during the surgery.