Introduction: The ureteral access sheath (UAS) has an important role in retrograde intrarenal surgery (RIRS), and its efficacy and safety in children has only been studied in small volume studies. Our study, the largest real-life global multicenter study in the literature, aimed to compare RIRS with and without UAS in different pediatric age groups. Methods: Anonymized data of 9 institutions that performed RIRS to patients younger than 18 years were involved to the study. Only the data of kidney stone surgeries between January 2015 and December 2020 were investigated retrospectively. Demographic characteristics of patients and stones, intraoperative and postoperative results were recorded. While analyzing the data, patients who underwent RIRS without UAS (no-UAS group) (n=195) and RIRS with UAS (UAS group) (n=194) were compared. Univariate and multivariate logistic regression analysis was performed to predict the risk of residual fragments. Results: Children in UAS group were found to be young, thin, and short (8.73 +/- 4.75 vs UAS 9.96 +/- 4.67 years, p<0.001; 119+/-29.8 vs 130+/-28.1 cm, p=0.021); 30.4 +/-18.9 vs 37.0 +/-19.2 kg, p<0.001), but there was no gender difference and similar symptoms were present at the initial presentation except hematuria, which was predominant in UAS group ((10.6% vs 17.3%, p<0.001). Concerning operative findings, no-USA group had smaller stone diameter (9.91 +/- 4.46 vs 11.59 +/- 4.85 mm, p=0.001), and shorter operation time (65.56 +/- 29.17 vs 73.38 +/- 36.80 min, p=0.040) and less stenting (35.7% vs 72.7%, p=0.003). Overall re-intervention rates for residual fragments and stone free rates (SFR) were similar between groups (p=0.5 & p=0.374). However, no-UAS group had significantly high re-RIRS (24.7% vs 13.5%, p=0.009). SFR found to have a positive correlation with smaller stone size and HLF usage compared to TFL in the univariate analysis (p < 0.001 & p=0.020), but multivariate analysis revealed only large stone size as a risk factor for residual fragments (p=0.001). Conclusions: RIRS can be performed safely in all patients with and without the use of UAS. In children of smaller size or younger age ( <5 years), limited use of UAS was observed in our study. UAS may be of greater utility in stones larger than 1 cm, regardless of the age of the children, and by using smaller diameter UAS and ureteroscopes we could decrease the number of complications. However, the use of UAS does not guarantee an improvement in the stone clearance rate. SOURCE OF Funding: NIL
