Three-dimensional mean stone density measurement is superior for predicting extracorporeal shock wave lithotripsy success.

Objectives: The objective of the present study was to investigate the usefulness of three-dimensional images of stones to measure mean stone density for predicting the outcome of shock wave lithotripsy.

Methods: We retrospectively identified 239 patients who underwent shock wave lithotripsy with pretreatment non-contrast computed tomography. We automatically measured the mean stone density of three-dimensional images of stones using a high-functional viewer. For comparison, mean stone density was also measured by two previously reported techniques using both the abdominal windows and the bone windows on the axial slice at the level of the largest diameter of the stone. We compared the outcome predictive power after the first treatment with outcomes according to measurement by four other methods. We also carried out logistic regression analysis, including mean stone density measured by three-dimensional images.

Results: The single treatment success rate was 48.5%. The effect size (14.148) of the mean stone density measured by three-dimensional images was higher than those of the other four manual methods. In addition, the area under the curve (0.6330) of the mean stone density measured by three-dimensional images was significantly higher than those of the other methods. Increasing stone volume (P = 0.002) and increasing mean stone density measured by three-dimensional images (P = 0.023) were significant independent predictors of the treatment outcome on multivariate analysis.

Conclusions: This is the first study to compare the predictive powers for shock wave lithotripsy outcome of various mean stone density measuring methods. There is an indication that mean stone density automatically measured by three-dimensional images of stones is more useful than other measuring methods for predicting outcomes of shock wave lithotripsy.