Comparison of Preoperative and Intraoperative Cultures for Predicting Postoperative Urinary Tract Infections Following Supine PCNL

Introduction: This study aimed to compare the predictive value of preoperative midstream urine culture (PMUC), intraoperative renal pelvic urine culture (RPUC), and stone culture (SC) for postoperative urinary tract infections (UTIs) following percutaneous nephrolithotomy (PCNL). Methods: We retrospectively analyzed 234 patients who underwent supine-PCNL between January 2020 and April 2025. UTI was diagnosed based on systemic inflammatory response syndrome criteria and elevated inflammatory markers. Demographic, peri-, intra- and post-operative data were compared between patients with and without UTI. Multivariate logistic regression identified independent predictors. Results: UTI occurred in 14.1%(n=33) of patients postoperatively, with 72.7% presenting with fever. Culture positivity rates were significantly higher in postoperative UTI-patients (PMUC=27.3%vs.7.5%, SC:39.4%vs.8.0% and RPUC:30.3%vs.6.0%; p<0.001). In UTI-patients, only 15.2% of postoperative urine cultures obtained before antibiotic treatment showed bacterial growth, which was lower than intraoperative cultures. UTI was higher in female patients (60.6% vs. 39.4%) and in those with an ASA score of 3 (p=0.001 and p=0.020). Female gender (OR=3.71, p=0.004), ASA-3 score (OR=5.13, p=0.029), positive SC (OR=5.83, p=0.001), and RPUC (OR=3.67, p=0.023) were independent predictors of postoperative UTI. PMUC was not associated (p = 0.65) with postoperative UTI in the multivariate analysis. Conclusions: Intraoperative SC and RPUC are superior to PMUC in predicting UTI after supine PCNL and should be routinely obtained. Female gender and ASA-3 score are independent risk factors. In patients who develop UTI, prior empirical or prophylactic antibiotic use may limit pathogen detection in postoperative urine cultures; therefore, intraoperative cultures play a critical role in early and targeted treatment.