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Ng CF et al, 2015: The effect of renal cortical thickness on the treatment outcomes of kidney stones treated with shockwave lithotripsy.

Ng CF, Luke S, Chiu PK, Teoh JY, Wong KT, Hou SS.
The S.H. Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China.
Department of Imaging and Intervention Radiology, The Chinese University of Hong Kong, Hong Kong, China.

Abstract

PURPOSE: Because the shock wave passes through various body tissues before reaching the stone, stone composition may affect the treatment efficacy of shock wave lithotripsy (SWL). We investigated the effect of various tissue components along the shock wave path on the success of SWL.
MATERIALS AND METHODS: From October 2008 to August 2010, a total of 206 patients with kidney stones sized 5 to 20 mm were prospectively recruited for a study of the factors that affect the outcome of treatment with a Sonolith Vision lithotripter. Successful SWL was defined as either stone-free status or residual fragments <4 mm at 12 weeks. Logistic regression analysis was performed to assess the factors that predicted treatment outcomes. Potential predictors included the patient's age, shock wave delivery rate, stone volume (SV), mean stone density (MSD), skin-to-stone distance (SSD), and the mean thickness of the three main components along the shock wave path: renal cortical thickness (KT), muscle thickness (MT), and soft-tissue thickness (ST).
RESULTS: The mean age of the patients was 53.8 years (range, 25-82 years). The overall treatment success rate after one session of SWL was 43.2%. The mean KT, MT, and ST were 26.9, 16.6, and 40.8 mm, respectively. The logistic regression results showed that a slower shock wave delivery rate, smaller SV, a lower MSD, and a thicker KT were found to be significant predictors for successful SWL. SSD, MT, and ST were not predictors of successful treatment.
CONCLUSIONS: Among the main tissue components along the shock wave path, a thicker KT was a favorable factor for successful SWL after adjustment for SV, MSD, and the shock wave delivery rate. 

Korean J Urol. 2015 May;56(5):379-85. doi: 10.4111/kju.2015.56.5.379. Epub 2015 Apr 28.

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Comments 1

Peter Alken on Tuesday, 22 September 2015 10:35

It says that the measurements were taken along the shock wave path. But in fact the authors had the same two problems as Pareek et al. (Shock wave lithotripsy success determined by skin-to-stone distance on computed tomography. Urology 2005; 66: 941–944) when they introduced the Skin-Stone-Distance (SSD) parameter: 1. CT images depict the body in a strictly axial plane but the shock wave path may enter the body in an oblique fashion and 2. It is impossible to determine the exact site of the shockhaed placement on the CT images either prospectively or retrospectively.
As a consequence - as Pareek et al.- the authors measured three distances (true posterior 0°, 45° lateral, and true lateral 90°) to calculate the mean values. And then statistics help to find correlations that sometimes can be confirmed by others and sometimes not depending on the different machines and technique used. It is difficult to imagine that the differences of the small renal cortex thickness KT, of 26.96±5.72 mm have a significant causal influence on the ESWL results.

It says that the measurements were taken along the shock wave path. But in fact the authors had the same two problems as Pareek et al. (Shock wave lithotripsy success determined by skin-to-stone distance on computed tomography. Urology 2005; 66: 941–944) when they introduced the Skin-Stone-Distance (SSD) parameter: 1. CT images depict the body in a strictly axial plane but the shock wave path may enter the body in an oblique fashion and 2. It is impossible to determine the exact site of the shockhaed placement on the CT images either prospectively or retrospectively. As a consequence - as Pareek et al.- the authors measured three distances (true posterior 0°, 45° lateral, and true lateral 90°) to calculate the mean values. And then statistics help to find correlations that sometimes can be confirmed by others and sometimes not depending on the different machines and technique used. It is difficult to imagine that the differences of the small renal cortex thickness KT, of 26.96±5.72 mm have a significant causal influence on the ESWL results.
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