Prediction of stone-free status and complication rates after tubeless percutaneous nephrolithotomy: a comparative and retrospective study using three stone-scoring systems and preoperative parameters.

Objective: To investigate the factors predictive of surgical outcomes of tubeless percutaneous nephrolithotomy (TPCNL) and to compare the predictability and accuracy of the Guy's stone score, S.T.O.N.E. nephrolithometry, and CROES nomogram.

Methods: We reviewed retrospectively the surgical outcomes recorded consecutively and imaging data of preoperative computed tomography scans of 141 patients who had undergone TPCNL from June 2012 to October 2015. Guy's, S.T.O.N.E., and CROES stone-scoring systems (SSSs) and other prognostic factors were assessed using univariate and multivariate statistical analyses.

Results: The initial stone-free and complication rates after TPCNL were 78.7 (111/141) and 17.0 % (24/141). On univariate analysis, all three scoring systems were identified as significant factors in terms of stone-free rate (SFR). The multivariate logistic regression analysis showed that the Guy's stone score and stone burden ≥385 mm2 had significant correlations with stone-free status [odds ratios (OR) = 3.220, p = 0.001 and OR = 6.451, p = 0.002, respectively]. Guy's stone score (OR = 1.879, p = 0.013) was an independent risk factor for the development of complications. The area under the receiver operating characteristic (ROC) curves for the Guy's, S.T.O.N.E., and CROES SSSs and stone burden showed good results (0.821, 0.816, 0.820, and 0.800, respectively). Pairwise comparison of ROC curves showed that there was no significant difference between each final score and stone burden.

Conclusions: Of the three scoring systems, Guy's stone score was the only significant predictive factor for SFR and complication rates after TPCNL in the multivariate logistic regression analysis. Stone burden was significantly associated with a postoperative stone-free status (SFS).