Non-contrast cine magnetic resonance urography in evaluating and monitoring of primary obstructive megaureter: a case series study.

Objective: To evaluate the feasibility and usefulness of cine magnetic resonance urography (MRU) as a novel examination for primary obstructive megaureter (POM).

Material and methods: The study was conducted on 44 patients with POM who underwent cine MRU from May 2020 to October 2022. Referring to the international system of vesicoureteral reflux, patients were divided into the low-risk (grade I-IV) and the high-risk (grade V) groups. From the ureterovesical orifice to the ureteropelvic junction, the ureteral contraction ratio was measured at every 10% of the total length of the ureter.

Results: A total of 44 patients and 53 ureters with POM who underwent cine MRU were included. The contraction ratios were lower in the high-risk group than those in the low-risk group, with significant differences at the distal 10% (12.91% vs 29.02%, p < 0.001) and 20% levels (16.50% vs 32.34%, p = 0.019). After surgery, the ureteral contraction ratios at the 10% and 20% levels have a significant improvement (42.05% vs 21.00%, p = 0.001; 52.30% vs 27.50%, p = 0.003). We further found the ureteral contraction ratio at the 10% level being as a predictor of surgical technique. When the ureteral contraction ratio at 10% level was less than 12.67%, reimplantation may be more appropriate (AUC = 0.900, p < 0.001; The Youden index = 0.800).

Conclusion: The ureteral contractile activity at different levels in cine MRU can be used to evaluate the severity and treatment effectiveness, and also have certain reference value for the selection of surgical methods. Larger, multicenter studies are warranted to validate these findings.