since the introduction of ESWL in treatment of renal stones, it remained the first option for most renal and ureteric stones, with a success rate ranging from 60% to 90%. Multiple variables can affect treatment outcome, including those related to the machine, dose administered, and factors related to the patient; the exact role of most of these factors is still under study.
We investigated the effect of shock wave frequency on treatment outcomes in terms of success and complication rates.
PATIENTS AND METHOD:
139 patients with radio-opaque renal stones, presented to the Urology consultancy clinic during the period June 2010 through January 2012 and decided to undergo ESWL treatment were randomized into three groups, the first group (46 patients) received shock waves at a frequency of 120 waves per minute, the second (47 patients) at 90 w/m, and the third group (46 patients) at 60 w/m. Patients were followed for treatment outcome and appearance of complications at 1 week, 3 weeks, and 6 weeks. Stone free status or insignificant asymptomatic residual gravels of 5mm or less are considered as success. Durations of hematuria and analgesic requirement were the main complications looked for during follow up, while subcapsular and retroperitoneal hematomas were looked.
All patients received 3500-4000 shock waves per session at 17-18 KV energy. Success rate was significantly higher in the second and third groups, while the durations of hematuria and analgesic requirement were significantly shorter in groups 2 and 3. There was no significant difference between groups 2 and 3 in all outcome and complication parameters; however, the duration of treatment was significantly longer in groups 2 and 3.
ESWL efficacy in fragmenting renal stones is significantly improved by decreasing frequency from the standard 120 sw/min to slower rates (90 and 60 sw/min), with significantly decreased analgesic requirement and hematuria durations. There were no significant differences between the 60 and 90 sw/min frequencies. Taking in account the longer treatment duration for the 60 sw/min frequency; the 90 sw/min frequency would be optimal in terms of stone disintegration, complications, and duration of treatment.