Concordance of renal stone culture: PMUC, RPUC, RSC and post-PCNL sepsis-a non-randomized prospective observation cohort study.

INTRODUCTION: Between 5 and 10% of patients undergoing percutaneous nephrolithotomy (PCNL) develop postoperative sepsis 1, 2. Strategies to prevent infectious complications are based on information provided by preoperative midstream urine cultures (PMUC). The aim of this study is to evaluate the concordance of the microbiologic findings of PMUC, cultures of the renal stone (RSC) and urine obtained directly from the renal pelvis (RPUC) in patients undergoing PCNL.

MATERIALS AND METHODS: This is a multicenter prospective study. The study included all patients who underwent PCNL from May 2013 to July 2015 in three academic hospitals. All patients underwent a PMUC. Samples for RPUC were obtained by renal puncture for PCNL. Stone fragments extracted during the procedure were sent for culture (RSC). Clinical variables, stone configuration, burden and microbiology reports of cultures were recorded. We analyzed concordance between cultures and association with infectious complications.

RESULTS: One hundred and twenty-two patients underwent PCNL. Twenty-four percent had positive culture, 3.2% (4/122) PMUC, 14.7% (18/122) RPUC and 13.9% (17/122) RSC. Positive PMUC demonstrated multidrug-susceptible Escherichia coli and Staphylococcus aureus, while RPUC showed multidrug-resistant pathogens and/or fungus. Seven patients (5.7%) developed postoperative infectious complications prior to discharge. There was a weak correlation between PMUC and intraoperative urine cultures (RPUC and RSC). Concordance rate between RPUC and RSC was 83.3%. The most common isolated pathogens were multidrug-resistant bacteria or fungus.

CONCLUSIONS: PMUC did not reflect the microbiological environment found in stones and urine directly obtained from the renal pelvis. Patients with postoperative infectious complications had negative PMUC with positive RPUC or RSC. RPUC and RSC can help guide prompt and appropriate antibiotic treatment for patients who develop postoperative infectious complications after PCNL.