Yamashita S. et al., 2019: Ureteral wall volume at ureteral stone site is a critical predictor for shock wave lithotripsy outcomes: comparison with ureteral wall thickness and area
Yamashita S, Kohjimoto Y, Iguchi T, Nishizawa S, Kikkawa K, Hara I.
Department of Urology, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Wakayama, 641-0012, Japan.
Department of Urology, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Wakayama, 641-0012, Japan.
Abstract
Our objectives were to compare measurements of ureteral wall area, ureteral wall volume and ureteral wall thickness for their use in prediction of shock wave lithotripsy outcomes. We retrospectively identified 218 patients that underwent shock wave lithotripsy for ureteral calculi with pretreatment non-contrast computed tomography. We measured ureteral wall thickness, ureteral wall area and ureteral wall volume by high functional viewer. Ureteral wall thickness was defined as the maximum thickness of ureteral wall, and ureteral wall area as the area of ureteral wall around the stone in the maximal stone diameter on axial computed tomography image. Ureteral wall volume was defined as the volume of ureteral wall from the upper to lower edge of the stone. Treatment success was defined as absence of residual fragments within 3 months after the first session. We compared the outcome predictive power among these parameters and logistic regression analysis to identify factors contributing to treatment failure. The treatment success rate was 47.6%. Ureteral wall thickness, ureteral wall area and ureteral wall volume in successful cases were all significantly smaller than those in unsuccessful cases (all p < 0.01). Area under curve of ureteral wall volume was the largest of these parameters and significantly larger than that of ureteral wall thickness (p < 0.01). On multiple logistic regression analysis, ureteral wall volume was the only significant independent predictor of treatment outcome. Ureteral wall volume is a better predictor of shock wave lithotripsy outcome than ureteral wall thickness or ureteral wall area.
Urolithiasis. 2019 Aug 23. doi: 10.1007/s00240-019-01154-w. [Epub ahead of print]
Comments 1
The 49, 3 % success rate of the present series is inexplicably low. In 2015 Sarica K et al. (1) did a very similar study on ESWL treatment of impacted proximal ureteral stones with a success rate of 78,4%. Among the predictive factors evaluated by them - ureteral wall thickness (UWT), diameter of the ureter proximal to the stone (PUD), renal pelvic anteroposterior diameter (PAPD) and stone density (HU) - only UWT and HU had a significant impact on the stone free rate in a multivariate analysis. A cut-off value of UWT > 3.55 mm was highly predictive of additional procedures to reach a completely stone-free status.
My comment was: The images accompanying the manuscript illustrated one problem to measure the ureteral wall thickness: the diameter of the ureteral wall is irregular and from the data given in the manuscript it was not clear where the measurements were taken. Probably more work has to be done to introduce the ureteral wall thickness as a reliable parameter to predict SWL success in such cases.
The authors of the present publication present a more sophisticated evaluation of the CT-images. They do not report on the time it takes to evaluate the CT images and the reproducibility of the measurements but it seems to be logical that UWV, is more precise in predicting SWL outcomes than UWT. More data from other groups are to be expected