Preoperative hydronephrosis is a predictive factor of ureteral stenosis after flexible ureteroscopy: a propensity scores matching analysis

Objectives Ureteral stenosis is a serious complication of flexible ureteroscopy. How to predict the possibility of stricture before surgery is an important topic. This research retrospectively studied the influence of preoperative hydronephrosis on ureteral stenosis after flexible ureteroscopy, to explore whether the preoperative hydronephrosis could predict postoperative ureteral stenosis. Methods We conducted a retrospective study on patients who received flexible ureteroscopy in our hospital for upper ureteral calculi from January 2015 to June 2018. Patients were followed-up for 36 months after surgery, and intraoperative and postoperative complications were recorded. We divided patients into the mild hydronephrosis group and moderate to severe hydronephrosis group. Preoperative clinical baseline data of the patients were adjusted by propensity matching score analysis. Differences of intraoperative ureteral injury, operative time, postoperative ureteral stricture, and SFR one month after surgery was statistically analyzed. Kaplan-Meier's method and Log-rank test were used to compare the differences in the cumulative incidence of ureteral stenosis between the two groups. Cox regression was used to compare the hazard ratio of ureteral stenosis between the two groups. Results A total of 447 patients with 469 sides surgery were included, including 349 sides in the mild hydronephrosis group and 120 sides in the moderate to severe hydronephrosis group. Twenty-nine patients with 30 sides developed ureteral stenosis. Before and after propensity, the incidence of ureteral stricture matching analysis was 6.4% and 8%, respectively. There were statistical differences in ureteral stricture and injury, but the statistical differences in SFR and operation time were inconsistent. Kaplan-Meier showed a significant difference in the cumulative incidence of ureteral stenosis between the two groups. Conclusions Patients with moderate to severe hydronephrosis before surgery were more likely to have an intraoperative ureteral injury and postoperative ureteral stricture after FRUS. Preoperative hydronephrosis is an important predictor of ureteral stricture.