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Sources of Funding: none.

Introduction

Although previous studies have indicated that stone heterogeneity can affect shock wave lithotripsy (SWL) outcomes, there is no established measurement of stone heterogeneity on non-contrast computed tomography (NCCT) imagery. We investigated whether variation coefficient of stone density (VCSD) can predict shock wave success.

Methods

We conducted a retrospective review of 245 patients with urinary calculi who had undergone SWL for upper urinary tract calculi. We compared discriminative powers for treatment success using receiver operating characteristics ROC analyses among three indices based on CT attenuation of the stone, i.e., mean stone density (MSD), standard deviation of stone density (SDSD) and VCSD. We also performed logistic regression analysis to identify factors contributing to treatment success. Treatment success was determined as absence or residual fragments <4mm using NCCT within three months after a first session of SWL.

Results

Treatment success rate was 47.8% (117/245 cases). From ROC analyses for treatment success, AUC of VCSD (0.71) was larger than that of MSD (0.64, p=0.09) and SDSD (0.54, p<0.01) (Figure). Multivariate analysis revealed that MDS (p=0.028) and VCSD (p<0.001) independently predicted the outcome (Table). Categorized by stone location, VCSD was the independent significant predictor for SWL outcomes in both kidney (p=0.047) and ureteral calculi (p<0.001).

Conclusions

We found that variation coefficient of stone density can be a novel predictor of SWL success. The development of nomograms or scoring systems including VCSD can assist in the decision process for patients and minimize unnecessary delay in treatment of urolithiasis.

Funding

none.