Comparison of STONE and CROES nephrolithometry scoring systems for predicting stone-free status and complication rates after percutaneous nephrolithotomy: a single center study with 262 cases

The aim of this study was to compare the accuracy 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 nephrolithometry scores' correlation with stone-free status, operation 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 underwent 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 experienced 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 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.