PCNL Stone Complexity — CT-Based Scoring
S.T.O.N.E. Parameters
Awaiting Selections
Select all 5 parameters from preoperative CT imaging.
Guidelines & Evidence
Verified
Last Review: 2026
When to Use
When to Use the S.T.O.N.E. Nephrolithometry Score
Preoperative planning and risk stratification for patients undergoing percutaneous nephrolithotomy (PCNL)
Prediction of stone-free rate (SFR) after a single PCNL procedure
Counseling patients regarding expected success rates and potential need for staged or auxiliary procedures
Surgical decision-making: choice of access (supine vs prone), number of tracts, and operative time estimation
Comparison of outcomes between different centers and surgeons
Research and audit of PCNL results
Selection between PCNL and alternative modalities (RIRS, SWL) in complex stones
Identifying high-complexity cases that may benefit from referral to high-volume endourology centers
Clinical Context
Percutaneous nephrolithotomy remains the gold-standard treatment for large renal stones (>2 cm), staghorn calculi, and stones with unfavorable anatomy for retrograde intrarenal surgery. Stone complexity significantly affects stone-free rates, operative time, radiation exposure, blood loss, and complication rates. The S.T.O.N.E. score was developed as a simple, reproducible, CT-based tool that quantifies five key parameters to predict PCNL outcomes more objectively than subjective judgment alone.
Advantages of S.T.O.N.E. Score
Based entirely on preoperative non-contrast CT (NCCT) — no additional imaging required
Quick and easy to calculate at the point of care
Good correlation with stone-free rates and surgical difficulty
Useful complement to Guy's Stone Score and other nephrolithometry systems
Helps standardize reporting of stone complexity in endourology literature
Last Comprehensive Review: 2026