1 3 Urolithiasis DOI 10.1007/s00240-016-0935-0 ORIGINAL PAPER Comparison of S.T.O.N.E and CROES nephrolithometry scoring systems for predicting stone-free status and complication rates after percutaneous nephrolithotomy: a single center study with 262 cases Serkan Yarimoglu 1 · Salih Polat 1 · Ibrahim Halil Bozkurt 1 · Tarık Yonguc 1 · Ozgu Aydogdu 1 · Erhan Aydın 1 · Tansu Degirmenci 1 Received: 29 April 2016 / Accepted: 2 November 2016 © Springer-Verlag Berlin Heidelberg 2016 and operation time. We demonstrated that S.T.O.N.E. and CROES scoring systems were useful for predicting post- PCNL stone-free status. But both scoring systems were not useful for predicting post-PCNL complications. Keywords CROES nephrolithometry score · S.T.O.N.E. nephrolithometry · Modified Clavien classification Introduction Percutaneous nephrolithotomy (PNL) has been recom- mended as the first-line treatment option for kidney stones that are either refractory to extracorporeal shock wave lith- otripsy (ESWL) or are >2 cm in diameter according to the guidelines of the European Association of Urology (EAU) [1]. The number of PCNLs has been increasing over the last decade and use of PCNL is expected to continue in the future. Differences in reporting of PCNL outcomes among the authors have recently lead to the invention of nephro- lithometry scoring systems using preoperative parameters to improved patient counseling, surgical planning, and evaluation of outcomes and uniform academic reporting [2]. The CROES nephrolithometric nomogram and the S.T.O.N.E. nephrolithometry scoring system have been described as predictors of stone-free status after PCNL by Smith and Okhunov, respectively [3, 4]. The CROES neph- rolithometric nomogram is a scoring system, which gives an estimated success rate in a range 30–90% depending on the stone burden, annual case volume, and prior stone treatment, presence of staghorn stone, stone location and stone count [4]. The S.T.O.N.E. nephrolithometry scoring system assesses PCNL complexity according to stone size, tract length, obstruction, number of involved calyces, and Hounsfield units calculated from the CT. According to the Abstract The aim of this study was to compare the accu- racy of the CROES nephrolithometric nomogram and S.T.O.N.E. scoring system in predicting PCNL outcomes in terms of stone-free rate, estimated blood loss (EBL), operative time (OR), length of hospital stay (LOS), and complications. Patients who underwent PCNL for renal stones between May 2012 and January 2015 were analyzed retrospectively. The patients’ demographic characteristics and operational features were recorded prospectively in all patients postoperatively. S.T.O.N.E. and CROES nephro- lithometry scores’ correlation with stone-free status, opera- tion and fluoroscopy time, length of hospital stay (LOS) and blood loss (BL) was evaluated. Patients were categorized according to S.T.O.N.E. nephrolithometry and CROES nephrolithometry scores. Postoperative complications were graded according to modified Clavien classification (Dindo et al. in Ann Surg 240:205–213, 2004) and the correlation of both scoring systems with postoperative complications was also evaluated. We identified 437 patients who under- went PCNL between May 2012 and January 2015. A total of 262 patients who are available data for the CROES and S.T.O.N.E. scoring systems were included in the recent study. The mean S.T.O.N.E score was 7.65 ± 1.56 and the mean CROES score was 191.13 ± 64.39. The overall stone-free rate was 71.4%. Of the 262 patients, 89 expe- rienced postoperative complications. Stone-free patients had significantly lower BMI (<0.001) and stone burden (p < 0.001). Regression analysis showed that both scoring systems were significantly associated with stone-free rates * Salih Polat salihpolat@gmail.com 1 Department of Urology, Izmir Bozyaka Training and Research Hospital, Karabaglar, Izmir, Turkey