Effect of Tissue Densities at the Skin-to-Stone Distance on the Success of Shockwave Lithotripsy

Abstract

Objective: There are several factors affecting the success of shockwave lithotripsy (SWL), which is still one of the first-line treatments for renal stones smaller than 2 cm. The aim of this study was to evaluate the effect of thickness and density measurements obtained by computed tomography (CT) for various tissues within the route of shockwaves on the outcome of SWL treatment success. Materials and Methods: The data of 89 patients who underwent SWL for renal pelvic stones smaller than 2 cm between July 2020 and September 2021 were prospectively evaluated. Age, sex, body mass index, stone volume, stone density, skin-to-stone distance, tissue thickness and density, hydronephrosis, number of shockwaves, and SWL success were recorded. Patients were divided into two groups according to SWL success: SWL success and SWL failure groups. Demographic data and CT parameters were compared between the groups. Results: Stone-free status (<4 mm residual stone) was achieved in 70 patients. Mean subcutaneous adipose tissue density was -97 Hounsfield unit (HU) in group 1 and -101 HU in group 2 (p=0.575). Mean muscle tissue density was 32 HU in group 1 and 31 HU in group 2 (p=0.843). Perinephric adipose tissue density was calculated as -93 HU in group 1 and -98 HU in group 2 (p=0.621). Skin-to-stone distance, tissue thickness, and tissue density findings failed to effect stone-free status. Conclusion: According to the results obtained in this study, tissue thickness and density in a CT scan did not affect treatment success. Only stone density and size in a CT scan can help to decide SWL treatment success, as suggested in previous studies.

Keywords

• hounsfield unit
• extracorporeal shockwave lithotripsy
• renal stone
• non-contrast computed tomography