External validation of the S.T.O.N.E. nephrolithometry scoring system

Area of Science:

• Nephrology
• Urology
• Surgical Outcomes Research

Background:

• Percutaneous nephrolithotomy (PCNL) is a key procedure for kidney stone removal.
• Accurate preoperative assessment is crucial for optimizing PCNL outcomes.
• The S.T.O.N.E. nephrolithometry scoring system was developed for this purpose.

Purpose of the Study:

• To externally validate the S.T.O.N.E. scoring system.
• To assess the correlation between S.T.O.N.E. scores and key PCNL outcomes.
• To compare the predictive accuracy of the S.T.O.N.E. score with other factors.

Main Methods:

• Retrospective review of 155 PCNL procedures performed between 2009 and 2013.
• Calculation of S.T.O.N.E. scores for each patient.
• Correlation analysis of S.T.O.N.E. scores with stone-free status, estimated blood loss (EBL), operative time, length of hospital stay (LOS), and complications.

Main Results:

• Higher S.T.O.N.E. scores correlated with lower stone-free rates (p=0.001), increased EBL (p=0.003), longer operative times (r=0.4, p<0.001), and extended LOS (r=0.3, p=0.001).
• The overall stone-free rate was 71.6%, and the complication rate was 15.5%.
• Complication rates did not correlate with S.T.O.N.E. scores (p=0.9).

Conclusions:

• External validation confirms the S.T.O.N.E. scoring system's utility in predicting PCNL outcomes.
• The system's accuracy in predicting stone-free status is comparable to stone size and number of involved calyces.
• The S.T.O.N.E. score is a valuable tool for preoperative assessment in PCNL.