Does a kidney stone culture make sense? The findings of microbiological cultures of kidney stones and correlation with stone composition, preoperative urine testing and postoperative SIRS

Abstract

Purpose: The study investigates the results of kidney stone cultures and its correlation with preoperative urine tests, stone composition and postoperative systemic inflammatory response syndrome (SIRS) in patients undergoing percutaneous nephrolithotomy (PCNL). Methods: Data from 338 PCNL procedures performed between January 2018 and September 2023 at two centers in the Netherlands were included for analysis. Preoperative urine tests, kidney stone analysis and the outcome of kidney stone cultures were evaluated in addition to general patient characteristics and surgical information. Preoperative urine tests and stone cultures were concordant if they were both negative or both positive with the same microorganism. Multivariable logistic regression evaluated factors associated with positive stone cultures and their relationship to postoperative SIRS. Results: Stone cultures were positive in 43% of cases and were concordant with preoperative urine tests in 66% of cases. Stone culture results identified 33 different microorganisms, extending beyond urease-positive bacteria: most commonly found were Enterococcus faecalis, Escherichia coli, and Proteus mirabilis. Positive stone cultures were found across all types of stone composition. Positive stone cultures were significantly associated with postoperative SIRS (OR 3.12, 95% CI 1.01–9.65) and a positive preoperative urine test was not (OR 1.60, 95% CI 0.56–4.53). Conclusion: Stone cultures provide additional microbiological insights to preoperative urine testing. All types of stone composition can be associated with positive stone cultures, questioning the current thinking of infection vs. non-infection stones.