First Worldwide Multicentric Series of Mini-Ecirs in Children: Outcomes from two Tertiary Endourology Centers.

Introduction: Endoscopic combined intrarenal surgery (ECIRS) is a combination of both retrograde and antegrade approaches for treatment of large or complex renal stones in one procedure, that are currently being treated with multiple tracts or sessions of percutaneous nephrolithotomy, increasing the complications. The aim of our study is to describe the clinical outcomes of Mini-ECIRS in a pediatric population. Material and Methods: A retrospective study was performed in pediatric patients with lithiasis disease treated with mini-ECIRS between 2006 and 2023 in 2 referral centers in Europe. Demographic data, clinical data, stone size and location, laser settings, intraoperative variables, stone-free rate (SFR) and complications were collected. Pearson's chi-squared test, Fisheŕs test and logistic regression, were performed. Results: A total of 32 mini-ECIRS were included. The mean age was 9,8 years, 56.3% girls. The mean size and volume of the stone were 21.5mm and 3298, 2mm 3 , 53.1% were multiple. Ureteral access sheath was used in 93.8% of the surgeries and only 37.5% had preoperative JJ stent. 53.1% of percutaneous access were with 14 Fr sheath. High power laser was the most frequent energy source for lithotripsy, including thulium fiber laser. The mean operative time was 166,6 minutes. There was one perforation of the collecting system that was managed with JJ stent and in the postoperative period 81.2% of the patients had no complications. Three presented fever, 1 developed urinary sepsis, and 1 required reintervention. The SFR was 75% and the size, volume, hardness, and complexity of the lithiasis, as well as the non-use of lithotripsy in the retrograde approach were statistically significant in decreasing the success of the surgery. Conclusions: ECIRS is a feasible, safe, and efficient procedure in children with complex renal lithiasis, decreasing the number of procedures needed for stone free. Multicenter studies are required to validate these results on a population scale.