Quantitative assessment of postoperative urinary jet dynamics after unilateral ureteral stricture reconstruction using non-contrast cine MR urography.

PURPOSE: To evaluate non-contrast cine magnetic resonance urography (MRU) for quantifying postoperative urinary jet dynamics in unilateral ureteral stricture disease (USD) and explore their relevance to ureteral functional recovery. METHODS: This prospective single-center study included 53 patients examined within 1 week before and 3 months after surgery. Five 60-s cine acquisitions were obtained per examination. Two radiologists assessed image quality and measured urinary jet frequency and injection duration. Intraclass correlation coefficients (ICCs) assessed interobserver agreement. Jet parameters were compared between affected and contralateral ureters before and after surgery, and their correlations were analyzed. RESULTS: Image quality and quantitative measurements showed excellent interobserver agreement (ICC = 0.895 and 0.910, respectively; both P < 0.001). Jet frequency and injection duration were lower in the affected than contralateral ureter before and after surgery (all P < 0.001) and increased in the affected ureter postoperatively (both P < 0.001). Contralateral jet frequency decreased modestly (P = 0.007), whereas injection duration did not change (P = 0.443). Frequency and duration were positively correlated under all conditions, most strongly in the preoperative affected ureter (r = 0.974, P < 0.001). CONCLUSION: Non-contrast cine MRU enabled quantitative assessment of postoperative urinary jet changes. Increased affected-side jet activity was consistent with improved ureteral urine transport and may provide indirect, complementary functional information during follow-up. Urinary jet parameters should not be considered standalone measures of complete recovery of ureteral function, and cine MRU should not replace CTU for anatomical evaluation.