Abstract
We read the study by Scotland et al. 1 entitled “Total Surface Area Influences Stone Free Outcomes in Shock Wave Lithotripsy for Distal Ureteral Calculi” published in Journal of Endourology Vol. 33, No. 8 with great interest. This study included 104 patients with distal ureteral stone, and the authors argued that total stone surface area was a predictor factor for extracorporeal shock wave lithotripsy (SWL) success in distal ureteral calculi. However, we have major concerns regarding the methodology and statistical design of the study.
This study included patients who had previously received medical expulsive therapy or were treated urgently by SWL, but they did not compare terms of these factors. Also we know that stone size, Hounsfield unit, and body mass index are important factor for SWL success. 2,3 However, in this study, although the demographic distribution of these factors was presented, the statistical analysis of their effects on SWL success was missing.
In addition, we wonder based on which statistical method the authors argued for the fact that >24 mm2 the total surface area increases SWL success. What is the sensitivity and specificity of this value? Although this study is valuable for reminding the SWL in distal ureteral stone management, we believe that multivariate analyses are needed to show the effect of total surface area on SWL success.