Outcomes of 6.3 Fr flexible ureterorenoscopy and laser lithotripsy for paediatric kidney stone disease: a multicentre international study from EAU endourology.

OBJECTIVES: Paediatric urolithiasis is increasing in prevalence, and flexible ureterorenoscopy and laser lithotripsy (FURSL) is increasingly used for its management. Miniaturisation of single-use flexible ureteroscopes may facilitate ureteric access in paediatric patients. The 6.3 Fr HugeMed is among the smallest single-use flexible ureteroscope available, but paediatric data remain limited. We evaluated the safety and efficacy of the 6.3 Fr scope in a multicentre paediatric cohort. PATIENTS AND METHODS: A retrospective cohort study was undertaken across six international centres. Consecutive patients aged ≤ 18 years undergoing FURSL with the 6.3 Fr HugeMed single-use ureteroscope were included. The primary outcome was the stone-free rate (SFR), defined as no residual fragments or residual fragments ≤ 2 mm on follow-up imaging. Secondary outcomes included operative time, complications graded by the Clavien-Dindo classification, and length of follow-up. Univariable and multivariable logistic regression were used to identify predictors of stone-free status. RESULTS: In total, 102 paediatric patients (59 male, 43 female; mean age 9.5 years, range 2-18) were included. Mean largest single stone diameter was 9.5 mm (SD 3.9) and mean cumulative stone burden was 11.8 mm (SD 7.1, range 4-50). Stones occupied multiple locations in 40 patients (39.2%). Pre-operative stenting was performed in 78.4% and a ureteric access sheath was used in 84.3%. Median operative time was 30.5 min (IQR 25-45). The overall SFR was 83.3% (85/102). SFR fell with increasing cumulative burden (95.7% for < 10 mm, 81.8% for 10-20 mm, 36.4% for > 20 mm; p < 0.001) and was higher for single- than multiple-location stones (93.5% vs. 67.5%; p = 0.001). On multivariable analysis, cumulative stone burden was the main independent predictor of stone-free status (adjusted OR 0.83 per mm, 95% CI 0.74-0.94; p = 0.003). Four complications occurred (3.9%), all Clavien-Dindo grade I-II, with no grade ≥ III events. CONCLUSIONS: FURSL using the 6.3 Fr HugeMed single-use flexible ureteroscope achieved a high SFR with low morbidity. Outcomes were principally determined by stone burden. These findings support the feasibility and safety of ultra-thin single-use flexible ureteroscopes and warrant prospective comparative studies.