Clinical Value of Stone Radiodensity and Size in Predicting the Outcome of Extracorporeal Shockwave Lithotripsy in Renal Stones

Abstract

Introduction: The success rate of Extracorporeal Shockwave Lithotripsy (ESWL) depends on multiple factors. A major cause of ESWL failure is an undesirable stone composition. Aim: The aim of this study was to evaluate the usefulness of measuring renal calculi attenuation values on unenhanced computerised tomography images as a predictor of the outcome of ESWL in patients with a single renal stone of 7-20 mm, located in the renal pelvis. Materials and Methods: This retrospective study was conducted on 151 patients with renal stone of 7-20 mm within the renal pelvis who were referred to the Tohid Hospital, Sanandaj, Iran during the time period between May 2011 and May 2015. Patients with a single stone of 7-20 mm located in the renal pelvis were included in this study. Patients with elevated creatinine levels (more than 2 mg/dL), single kidney, obstructed kidney stones more than 20 mm and stones elsewhere in the collecting system were excluded from the study. For all patients Non-Contrast Computerised Tomography (NCCT) and ESWL was performed. Stone density, stone size and stone free rate were measured. Successful treatment of renal stones was defined as those patients who were stone free or were asymptomatic i.e., clinically insignificant residual fragments ≤4 mm in diameter, as measured by KUB X-ray and sonograhy three months after ESWL. The patients were further analysed by dividing them into six groups according to the stone density. All ESWLs were undertaken by STORZ SLK Lithotripter with fragmentation performed under fluoroscopic guidance. Data were analysed using SPSS statistical software version 18.0 and Chi-square test was also used. Results: The results showed that the ESWL success rate in patients with small stone size and high stone radiodensity was (n=10, 52.6%), while in patients with large stone size and high stone radiodensity it was (n=4, 36.4%). There was a significant difference between the success rate of lithotripsy and stone radiodensity (p-value=0.0002). Conclusion: The findings of the present study showed that stone radiodensity and stone size were useful parameters to predict the outcome of ESWL. We found a direct relation between the stone radiodensity and ESWL success rate. In addition, the results of our study showed that ESWL success rate in patients with small stone size (7-14 mm) was clinically remarkable. Considering these two parameters in conjunction with other stone parameters to select appropriate procedure is suggested.

Keywords

• densitometry
• kidney calculi
• treatment outcome