Can we successfully predict the outcome for extracorporeal shock wave lithotripsy (ESWL) for medium size renal stones? A single-center experience

Extracorporeal shock wave lithotripsy (ESWL) is one of the most used modalities in treatment of renal stones, but its effectiveness can be influenced by many factors related to the patient or the stone itself which may affect the success of stone disintegration. The aim of our study was to investigate the predictive value of some patient and stone-related factors for ESWL success for renal stones.A total of 100 patients with single radiopaque renal stone 10-20 mm in diameter, undergoing ESWL were enrolled in this study. All patients had non contrast computed tomography (NCCT) done before ESWL. We evaluated body mass index (BMI), skin-to-stone distance (SSD), stone size and Hounsfield density comparing these values between stone free (SF) and residual stone (RS) groups.Of the 100 patients, 70% had successful disintegration. There was no significant difference between stone free (SF) and residual stone (RS) groups as regard age or BMI. Meanwhile, there was a significant difference between SF and RS groups as regard stones' density and SSD, with higher values in RS group but there was statistically insignificant difference as regard stone size (p = 0.522). Using logistic regression analysis, we found that Hounsfield unit (HU) was better in predicting successful disintegration than SSD but without statistical significance.HU and SSD are the independent predictive factors for ESWL outcome, and they should be considered when planning ESWL in treatment of medium size renal stones.