Role of pre-operative ureteral stent on outcomes of retrograde intra-renal surgery (RIRS) in children. Results from a comparative, large, multicenter series.

<bold>Objective: </bold>To assess outcomes of pre-stenting versus non-pre-stenting in children undergoing retrograde intrarenal surgery (RIRS) for intrarenal stones.<bold>Methods: </bold>Children/adolescent with kidney stones undergoing RIRS in 9 centers between 2015-2020 were retrospectively reviewed.<bold>Exclusion Criteria: </bold>ureteral lithotripsy, bilateral procedures. Stone-free status was evaluated at 3-month and defined as a single residual fragment (RF) ≤2 mm/absence of multiple fragments. Patients were divided into two groups (Group 1 no-pre-stenting; group 2 pre-stenting). Student's, Chi-square and Fisher's exact test was used to assess difference between groups. Univariable and multivariable logistic regression analysis were performed to predict RF. Statistical significance: p-value <0.05.<bold>Results: </bold>389 children/adolescents were included (192 patients in Group 1). Pre-stented patients were younger compared with non-pre-stented (mean age 8.30±4.93 vs 10.43±4.30 years, p<0.001). There were no differences in stone characteristics (number, size, locations). Lasing and total surgical time were similar. Urinary tract infections were more prevalent in Group 2 (10.7%) compared to Group 1 (3.7%,p=0.016). Sepsis occurred in 2.1% of patients in Group 2 and no patient in Group 1 (p=0.146). 30.7% patients in Group 1 and 26.4% in Group 2 had RF (p=0.322). In univariate logistic regression analysis, stone size was associated with RF (OR 1.12 95%CI 1.06-1.18,p<0.001), whereas Thulium fiber laser with a lower incidence (OR 0.24 95%CI 0.06-0.69,p=0.020). Multivariate logistic regression analysis showed that stone size was associated with RF (OR 1.20 95%CI 1.08-1.36,p=0.001).<bold>Conclusions: </bold>RIRS showed similar stone-free rate in pre and non-pre-stented children/adolescents, although pre-stented patients were younger. A higher risk of post-operative infections was reported in pre-stented patients. [ABSTRACT FROM AUTHOR]