Prospective evaluation of outcome of percutaneous nephrolithotomy using the 'STONE' nephrolithometry score: A single-centre experience

Muhammad Farhan, Syed M Nazim, Basit Salam, M Hammad Ather, Muhammad Farhan, Syed M Nazim, Basit Salam, M Hammad Ather

Abstract

Objective: To assess the prediction of stone clearance and complications of percutaneous nephrolithotomy (PCNL) using the 'STONE' nephrolithometry score, assessing stone size, tract length (skin-to-stone distance), degree of obstruction, number of calyces involved and stone essence (density).

Patients and methods: This was a prospective study of patients undergoing single-tract PCNL while prone, conducted at a university hospital. All patients had non-contrast-enhanced computed tomography within 3 weeks of the procedure. Only patients with a unilateral procedure and radio-opaque stones were included. The five variables of the STONE nephrolithometry score were calculated before the procedure. The stone-free rates were assessed with a plain abdominal film at 4 weeks and complications were graded using the modified Clavien system.

Results: In all, 107 patients were included in the final analysis. Overall, 80% of patients were rendered stone-free. Among the individual variables, a larger stone (P = 0.002) and the involvement of multiple calyces (P = 0.04) were associated with residual stones, while tract length (skin-to-stone distance), stone density and presence of hydronephrosis were not. Patients who were rendered stone-free had a statistically significant lower overall STONE score than those with residual stones, at 7.24 vs. 8.14 (P = 0.02). The score also correlated with operative duration, which was significantly longer with a higher STONE score (P = 0.03). The complication rate was 18% and most complications were Clavien grade 2, with bleeding requiring a blood transfusion (11 patients) being the commonest. There were no deaths within 30 days of surgery, but there was no correlation between the STONE score and complications.

Conclusion: The STONE nephrolithometry score is a simple and easy to apply system for predicting complexity in stone clearance with PCNL.

Keywords: BMI, body mass index; CROES, Clinical Research Office of the Endo-Urological Society; NCECT, non-contrast-enhanced CT; Outcome; PCNL, percutaneous nephrolithotomy; Percutaneous nephrolithotomy; SFR, stone-free rate; Scoring system; Urolithiasis.

Figures

Figure 1
Figure 1
A plot of the relationship between the individual STONE scores and the SFR.

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Source: PubMed

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