Urinary Tract Infectious Complications After Retrograde Intrarenal Surgery: The RIRS-STAMP Risk Score from a Two-Center Cohort

Introduction: Postoperative infectious complications following retrograde intrarenal surgery (RIRS) remain a significant clinical challenge due to their potential progression to sepsis. This study aimed to identify perioperative risk factors associated with infection and to develop a practical risk stratification model. Materials and Methods: A total of 1949 patients who underwent RIRS in two centers between 2014 and 2025 were retrospectively analyzed. Patients were grouped according to irrigation method, and infectious outcomes including febrile urinary tract infection (UTI), sepsis, and septic shock were evaluated. Multivariable logistic regression analysis identified independent predictors of postoperative infection. Results: Overall, infectious complications occurred in 158 patients (8.1%), with no significant difference in total infection rates between the two groups. In the overall cohort, older age (OR 1.01; p = 0.045), preoperative JJ stenting (OR 1.48; p = 0.038), longer operative time (OR 1.01; p = 0.049), and a history of preoperative UTI requiring antibacterial treatment (OR 68.45; p < 0.001) were independent predictors of postoperative infection. These variables informed the development of the RIRS-STAMP score; the final combined model showed good discrimination (AUC 0.84, 95% CI 0.80–0.88) and was internally validated using 1000 bootstrap resamples. Discussion: These findings highlight the multifactorial nature of infection risk after RIRS and emphasize the importance of both host factors and procedural dynamics in infection development. The RIRS-STAMP score was developed based on these findings. Conclusions: The model can enable early identification of high-risk patients and supports individualized perioperative management; however, prospective external validation is required before routine clinical use.