Utility of S.T.O.N.E Score to Predict Stone Clearance After Percutaneous Nephrolithotomy

Naresh Kumar, Ahmad Nawaz, Mahtab Memon

Abstract

Objective

To determine the utility of S.T.O.N.E score in predicting the stone free rate (SFR) after percutaneous nephrolithotomy (PCNL).

Study design

Cross sectional study.

Place & Duration of study

Department of Urology, Jinnah Postgraduate Medical Centre (JPMC) Karachi, from January 2019 to November 2019.

Methodology

Patients, who had renal calculus of more than 1.5cm were included in this study. All patients had pre-procedure non contrast enhanced CT scan to determine the stone characteristics. S.T.O.N.E score was calculated using CT findings. In all patients, PCNL was performed by using rigid nephroscope in prone position. After three months of PCNL, CT scan was performed to determine stone free rate (SFR).

Results

Total of 120 patients were included in this study. The mean age of the patients was 39.2±11.2 year. There were 83 (69.2%) males and 37 (30.8%) females. After PCNL, 98 (81.7%) patients were stone free. In 22 (18.3%) patients residual stones found on follow up. Patients with residual stones had higher mean S.T.O.N.E score when compared to patients who had complete stone clearance which was significant (p <0.001). Binary logistic regression showed significant regression co-efficient (B=-0.40) and p-value <0.001. On ROC analysis, area under the curve (AUC) was 0.781 with 0.697 lower and 0.871 upper limits, which shows that S.T.O.N.E. score can clearly predict unsuccessful stone clearance.

Conclusion

S.T.O.N.E score can successfully predict risk of failure of PCNL in patients with renal stone disease. S.T.O.N.E. score is easy to calculate and can effectively help to predict high risk patients.

Key words

Urolithiasis, S.T.O.N.E. score, Stone free rate, Renal calculus.