S.T.O.N.E. Nephrolithometry: Novel Surgical Classification System for Kidney Calculi

To, first, propose a novel scoring system to standardize reporting for percutaneous nephrolithotomy because the instruments currently available to predict the percutaneous nephrolithotomy outcomes are cumbersome, not validated, and of limited clinical utility; and, second, assess and predict the stone-free rates and perioperative parameters applying S.T.O.N.E. nephrolithometry.Five reproducible variables available from preoperative noncontrast-enhanced computed tomography were measured: stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E).A total of 117 patients were included. The mean score was 7.7 (range 4-11). The stone-free rate after the first procedure was 80%. There were 18 complications (21%). The most frequent complications were postoperative sepsis and bleeding. The S.T.O.N.E. score correlated with the postoperative stone-free status (P = .001). The patients rendered stone free had statistically significant lower scores than the patients with residual stones (6.8 vs 9.7, P = .002). Additionally, the score correlated with the estimated blood loss (P = .005), operative time (P = .001), and length of hospital stay (P = .001).The novel scoring system we have presented was found to predict treatment success and the risk of perioperative complications after percutaneous nephrolithotomy. Reproducible, standardized parameters obtained from computed tomography imaging can be used for preoperative patient counseling, surgical planning, and evaluation of surgical outcomes across institutions and within medical studies.