Evaluation of the Optimal Frequency of and Pretreatment with Shock Waves in Patients with Renal Stones

PURPOSE: Many studies have been carried out to increase the success rate of shock wave lithotripsy (SWL) and to reduce renal injury. We investigated the success rate after one session as well as urine N-acetyl-β-d-glucosaminidase (NAG) levels for the evaluation of renal injury according to shock wave frequency and pretreatment with low-energy shock waves during SWL. MATERIALS AND METHODS: The study targeted 48 patients with renal stones who had undergone SWL. Patients were sequentially allocated into four groups according to shock wave frequency (60 or 120 shocks/min) and whether pretreatment had occurred. We documented total SWL operating number, success rate after first SWL, urine NAG, compliance, and the total cost for each patient. RESULTS: There were 32 males and 16 females with an average age of 51.6 years. The average stone size was 7.06 mm, and there was no significant difference in stone size between the groups. The data showed that patients treated with a frequency of 60 shocks/min had a lower mean number of SWL sessions, 1.36 sessions for 60 shocks/min and 2.0 sessions for 120 shocks/min, respectively, which was statistically significant (p<0.05). When comparing NAG/creatinin ratios before and after SWL between those with and without pretreatment, there was no significant difference according to pretreatment (p=0.406). CONCLUSIONS: SWL treatment at a frequency of 60 shocks/min yielded better outcomes, such as a lower number of SWL sessions, and had an increased success rate compared with SWL at 120 shocks/min. On the other hand, pretreatment did not impact renal injury. Therefore, SWL treatment at a frequency of 60 shocks/min could improve treatment efficacy more than that for SWL at 120 shocks/min.