Triple D Score Is a Reportable Predictor of Shockwave Lithotripsy Stone-Free Rates

Abstract

Over the last decade, shockwave lithotripsy (SWL) success rates have been correlated with stone density, skin-to-stone distance (SSD), and stone diameter. However, time constraints and the technical challenge of manual measurement often preclude utilization of these parameters. In this study, we describe a scoring system that accurately predicts SWL stone-free rates, is simple to calculate, and can be easily included in the radiology report. Two hundred thirty-five patients who underwent SWL from 2011 to 2014 were evaluated. One hundred thirty-three had available preoperative imaging. Stone density, SSD, ellipsoid stone volume (ESV), and stone-free rates were determined. Receiver operator characteristic (ROC) curves were generated to determine cutoff values for each parameter. The Triple D Score was calculated based upon the number of cutoff values a stone fell below. One hundred forty of the 235 patients (59.5%) who underwent SWL were stone free after single-session treatment. Seventy-six of the 133 (57.1%) patients with available preoperative imaging were stone free. ESV, SSD, and stone density were significant predictors of SWL success. Based upon the ROC curves, cutoffs of <150 μL for ESV, <12 cm for SSD, and <600 HU for stone density were established. A Triple D Score of 0, 1, 2, and 3 correlated with SWL success rates of 21.4%, 41.3%, 78.7%, and 96.1%, respectively. Readily available predictive tools are necessary to enhance SWL cost-effectiveness. The Triple D Score is simple to calculate and can be reported by radiologists. Incorporation of the Triple D Score into preoperative planning may increase the overall SWL success rates.