Reply letter to: Gorgotsky I, Shkarupa D, Shkarupa A et al. A Feasibility of Percutaneous Nephrolithotomy in Positive Urine Culture: A Single Center Retrospective Study

We read with interest the study by Gorgotsky et al(1) regarding the outcomes of percutaneous nephrolithotomy (PCNL) performed in patients with preoperative positive urine culture. The authors concluded that infected urine is not an independent risk factor of post-operative infectious complications after PCNL in low risk patients with (non-obstructive) kidney stones. They also suggested that a 24-hours antibiotic administration before the surgery can be considered as alternative to 1-week treatment and allow to perform PCNL with sufficient safety in selected patients. These considerations, especially in low infectious risk population with sterile urine culture, can be also borrowed from the randomized control trial from the EDGE Consortium(2) that demonstrated no advantage to providing 1 week of preoperative oral antibiotics in PCNL candidates. These results are in line with antimicrobial stewardship recommendations orientated in reducing antibiotic treatment duration in the antibiotic resistance era. As underlined by Gorgotsky et al1, EAU Guidelines states that an obstructed kidney with all signs of urinary tract infection (UTI) is a urological emergency(3) and instrumentation in the setting of an active infection can lead to an increased risk of post-procedural UTI. However, a positive urine culture does not imply necessarily an active UTI. The fundamental point is to distinguish between symptomatic UTI and asymptomatic bacteriuria (ASB) and, in patients with indwelling ureteral stent or nephrostomy tube, a bacterial colonization. This difference can be figured out by the integration of urine microscopy, complete blood count and C-reactive protein results. As recently stated by the Best Practice Statement on Urologic Procedures and Antimicrobial Prophylaxis(4), ASB does not need to be managed any differently prior to high-risk procedures (like PCNL) as single-dose antibiotic prophylaxis (AP). In the current study, the AP was continued in both groups for 3 days, in contrast with the intrinsic concept of prophylaxis and with the current urological guidelines that recommended single dose or 24hours duration. We know from the literature that bacteria can be cultured from the stones themselves in a variable rate (ranging from 15 to 70%)(5) and these results may be underestimated because stone culture is not routinely performed. In our experience, even when preoperative positive urine cultures were treated appropriately, the stone cultures revealed the same pathogen with similar resistance in the 63,6% of cases (article in press), implying that the pathogen is harbored inside the stone. In this study, the infectious complications, especially in group 2, are not correlated with intra-operative (i.e. stone culture) or post-operative blood and urine culture results, neglecting the possibility to evaluate the effect of antibiotic therapy on peri-operative cultures. Moreover, it would have been useful to report the biochemical analysis of the fragments to evaluate the rate of struvite stones in the group 2 of this low risk population for infectious complications. The authors excluded from the cohort all patients with potential pre-operative risk factors for infectious complications, except the presence of a urinary diversion like nephrostomy or ureteric stent and history of recurrent UTI, potential factors for bacterial colonization. Some intraoperative potential risk factors for infectious complications were not investigated as multiple percutaneous tracts, drainage of purulent urine during the puncture and the intrarenal pressures. A prolonged use of antibiotics can be associated with an increased risk of acquiring antibiotic-resistance and, in the setting of kidney stones, can be useless because any calcified or non-calcified stone may be colonized by infectious organisms creating a persistent bacterial niche. In this view, the results by Gorgotsky et al1 may help to reduce the rise of antibiotic resistance, avoiding pre-operative unnecessary treatments. The unsolved question remains how to efficiently treat the patients with risk factors for infectious complications, as they represent a considerable part of the population (34.5% in the series by Gorgotsky et al1). Future large prospective studies are needed to comprehensively investigate the impact of AP on patients that are candidate to stone removal with and without risk factors for infectious complications, both with ASB and negative urine culture.