Impact of lower pole stone location on outcomes of paediatric flexible ureteroscopy: results from a large endourology multicentric cohort study

INTRODUCTION: Management of lower pole (LP) stones in paediatric patients remains challenging due to anatomical factors that may limit stone clearance. This multicentre study evaluated the impact of stone location (LP vs non-LP) on perioperative outcomes and stone-free rates (SFR) following flexible ureteroscopy (fURSL), and identified independent predictors of procedural success. MATERIALS AND METHODS: We retrospectively analysed paediatric patients undergoing fURSL for urolithiasis between September 2015 and May 2025 at four tertiary referral centres. Demographic, radiological, intraoperative, and postoperative variables were collected. Patients were stratified according to stone location (LP vs non-LP). The primary outcome was SFR, defined as absence of residual fragments ≥2mm on postoperative ultrasonography at 3-month follow-up. Statistical analyses included Student's t-test, Mann-Whitney U test, and Chi-square/Fisher's exact test, as appropriate. Multivariable logistic regression was performed to identify independent predictors of LP location and SFR. Statistical significance was set at p<0.05. Operative time was significantly longer in LP cases, with a mean increase of 13.0 minutes (p<0.001). Although intraoperative visual stone-free rates were higher in LP procedures (71.0% vs 52.2%, p<0.001), postoperative ultrasound-confirmed SFR was lower (67.2% vs 81.5%, p<0.001). LP procedures were associated with higher complication rates (21.5% vs 13.3%, p=0.001), increased need for secondary procedures (12.9% vs 4.1%, p<0.001), and longer hospital stay (1.6 ± 0.7 vs 1.3 ± 0.7 days, p<0.001). On multivariable analysis, preoperative stenting (OR 3.80, 95%CI 1.90-7.59, p<0.001) and longer operative time (OR 1.04/min, 95%CI 1.03-1.05, p<0.001) independently predicted stone-free status, while LP location did not (OR 0.44, 95%CI 0.14-1.22, p=0.13). CONCLUSIONS: Although LP stones require longer procedures and are associated with lower ultrasound SFR, stone location alone does not independently predict treatment success. Optimised preoperative stenting and meticulous intraoperative technique may mitigate anatomical challenges and improve outcomes in paediatric LP stones.