S.T.O.N.E Score versus Guy’s Stone Score in the Prediction of Stone Clearance in Percutaneous Nephrolithotomy: A Cross-sectional Study

Abstract

Introduction: Percutaneous Nephrolithotomy (PCNL) has become the standard of care for large renal calculi. The aim of the surgery is to achieve maximum stone clearance with minimal postoperative complications. Various scoring systems have been described to predict both of these outcomes. S.T.O.N.E. Score and Guy's Stone Score (GSS) are two of the most widely used scoring systems. S.T.O.N.E. Score comprises of Size of the stone, Tract length, degree of Obstruction of the urinary system, Number of stones, and Essence. Aim: To compare the predictive power for stone clearance and postoperative complications of the two scoring systems, namely S.T.O.N.E. Score and GSS. Materials and Methods: This cross-sectional study was conducted at the Department of Genitourinary Surgery at Government Medical College, Kottayam, Kerala, India from March 2019 to August 2020. All patients above 18 years undergoing PCNL were included. A total of 122 patients were studied by calculating the preoperative S.T.O.N.E. Score and GSS and comparing them with post-PCNL stone clearance and complications. The association of both S.T.O.N.E. Score and GSS with stone clearance was estimated by plotting the Receiver Operating Curve (ROC) curve using Statistical Package for Social Sciences (SPSS) version 20, International Business Machines (IBM) SPSS Statistics windows, version 20.0 (Armonk, NY: IBM Corp.). A p-value <0.05 was considered statistically significant. Results: The mean age of the subjects was 49.8±12.47 years. A total of 76 males and 46 females were included in the present study. The mean S.T.O.N.E. Score among the study subjects was 7.12±1.57, and the mean GSS was 2.09±0.48. Complete stone clearance was achieved in 96 (78.7%) patients. A total of 22 (18%) patients had postoperative complications. Both scores had a significant association with stone clearance (p<0.001 for both) and postoperative complications (p-value for S.T.O.N.E. Score was 0.019 and GSS was 0.007). Conclusion: Both the S.T.O.N.E. Score and GSS can predict post-PCNL stone clearance and complications with comparable efficacy