Retrograde Intrarenal Surgery Using a Flexible Ureterorenoscope in Children With Urolithiasis; 儿童尿路结石病的柔性输尿管肾镜逆行肾内手术; Ретроградная интраренальная хирургия с использованием гибкого уретерореноскопа у детей с мочекаменной болезнью

BACKGROUND: Extracorporeal shock wave lithotripsy remains the first-line therapy in children with renal stones up to 2 cm. Recently, retrograde intrarenal surgery has become an alternative technology for fragmenting stones located in the renal pelvis and calyces. AIM: The work aimed to perform a retrospective analysis of the outcomes and complications of flexible ureterorenoscopy in children with urolithiasis. METHODS: The study included 63 children (65 renal units) who underwent retrograde intrarenal surgery. A total of 70 procedures were performed, including nephrolithotripsy in 59 cases (84.3%) and flexible ureterolithotripsy in 4 cases (5.7%). Nephrolithoextraction and ureterolithoextraction with a flexible endoscope were also performed. Stone size, volume, and density were assessed. The statistical association between the stone-free rate after retrograde intrarenal surgery and other parameters was analyzed using the Mann–Whitney test, Spearman correlation, and logistic regression. RESULTS: The median age of the patients was 11.8 years. Computed tomography revealed a median stone size of 13.2 mm and density of 1481 HU. After primary retrograde intrarenal surgery, complete stone clearance was achieved in 49 children (77.81%); after repeat intervention for residual fragments, the overall stone-free rate reached 93.66% (59 patients). Only 2 patients (3.17%) developed ureteral colic due to residual ureteral fragments after stent removal, requiring urgent intervention. Statistically significant predictors of residual fragments included initial stone size >1.6 cm on computed tomography and simultaneous stone location in both the pelvis and calyx (p < 0.05). No association was found between stone-free rate and patient age. CONCLUSION: The method of retrograde intrarenal surgery in children demonstrated a high stone-free rate and a low incidence of significant complications. © 2025 Elsevier B.V., All rights reserved.