Impact of prior shock wave lithotripsy on outcomes of retrograde intrarenal surgery for 1-2 cm lower pole kidney stones: a comparative analysis by the EAU-YAU Endourology & Urolithiasis Working Group.

Introduction: The study compared the outcomes of retrograde intrarenal surgery (RIRS) performed as a second-line treatment following failed extracorporeal shock wave lithotripsy (SWL) with those of primary RIRS in patients with 1-2 cm lower pole kidney stones. Material and methods: A total of 83 patients who underwent RIRS for 1-2 cm lower pole renal calculi between February 2019 and September 2024 were retrospectively analyzed in this single-center study. Patients were divided into two groups: those who underwent RIRS after failed SWL (n = 43) and those who underwent primary RIRS (n = 40). Preoperative demographics, stone characteristics, operative parameters, and postoperative outcomes were compared. Statistical analyses were performed using R software. Results: There were no significant differences between the groups in terms of age, gender, body mass index, stone size, laterality, density, or Ito scores. The failed SWL group had significantly longer operative time (60 [55-75] vs 55 [40-66] min, p = 0.041), RIRS time (45 [37.5-55] vs 40 [30-46] min, p = 0.043), and fluoroscopy time (4 [3-7] vs 2 [2-4] s, p = 0.001). The stone-free rate was lower in the failed SWL group (79% vs 92%), but the difference was not statistically significant (p = 0.153). Postoperative urinary tract infections and complication rates were similar between groups (p >0.05). Conclusions: RIRS remains an effective and safe option for managing lower pole kidney stones after failed SWL. However, previous SWL may increase procedural complexity, as reflected by longer operative and fluoroscopy times. Given the retrospective single-center design and limited sample size, the study's findings should be considered exploratory and interpreted with appropriate caution pending validation in larger, multicenter cohorts.