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Triple D Score Predicts Stone Free Rates Following Shockwave Lithotripsy
Timothy Tran, MD, Kathyrn McGillen, MD, Eugene Cone, BA, Shadi Al Ekish, MD, Damian Dupuy, MD, Gyan Pareek, MD.
Brown University, Providence, RI, USA.
BACKGROUND:
The cost effectiveness of stone treatment is paramount in an accountable care system. Over the last decade, numerous studies have suggested improved shockwave lithotripsy (SWL) success rates with consideration of stone density, skin-to-stone distance and stone diameter. However, due to time constraints and the technical challenge of manual measurement, it is often difficult to utilize these parameters in pre-operative planning. A scoring system combining these three measures has previously been shown to predict SWL treatment outcomes in upper ureteral calculi. Here, we utilize a similar scoring system and demonstrate it to be an accurate predictor of renal and ureteral calculi SWL success that is simple to calculate and can be easily reported as part of the radiographic findings.
METHODS:
A retrospective review was performed of 186 consecutive patients that underwent SWL from April 2011 to May 2012 at our institution. 84 had available pre-operative imaging. Stone density based upon Hounsfield units (HU), skin-to-stone distance, ellipsoid stone volume and stone-free rates were determined for all patients. Receiver operator curves (ROC) were generated to determine the optimal cutoff values for each statistically significant parameter. Each targeted stone was then assigned a score based upon whether its density, skin-to-stone distance and volume dimensions were above or below the established cutoff values (Triple D score).
RESULTS:
116 of the 186 patients (62.3%) that underwent SWL were stone free. 52/84 (61.9%) of the patients with available pre-operative imaging were stone free. In univariate analysis, ellipsoid stone volume and stone density were significant predictors of SWL success while skin-to-stone distance trended towards significance. Based upon the ROC curves, cutoffs of <150 μl for ellipsoid stone volume, <12 cm and <600 HU for stone density were established and the Triple D score was generated based upon the number of met criteria for each stone. A Triple D score of 0, 1, 2, and 3 had SWL success rates of 40.0%, 51.5%, 71.4% and 93.3%, respectively.
CONCLUSIONS:
Readily available predictive tools are necessary to enhance SWL cost effectiveness. Our data reveals that the Triple D Score can predict stone free-rates following SWL in renal stones. This score is simple to calculate and can be readily reported by radiologists with imaging studies. Incorporation of the Triple D score into pre-operative planning may increase overall SWL success rates.
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