Does a slower treatment rate impact the efficacy of extracorporeal shock wave lithotripsy for solitary kidney or ureteral stones?

Purpose: We compared the efficacy of an SR (70 to 80 shocks per minute) and an FR (120 shocks per minute) for ESWL for solitary stones less than 2 cm located in the kidney or proximal ureter. Materials and Methods: A total of 349 patients with a solitary, radiopaque kidney or ureteral stone underwent ESWL on a DoLi (R) 50 lithotriptor. Patients were grouped based on stone size, stone location and whether SR or FR treatment was performed. Of the 349 patients 135 had a renal stone between land 2 cm, 137 had a renal stone less than I cm and 77 had a proximal ureteral stone with a surface area of between 30 and go mm(2). SFRs were determined at approximately 1 month by plain x-ray of the kidneys, ureters and bladder. Results: In comparison to the FR groups SR groups required fewer shocks and had significantly lower power indexes. Of patients with renal stones between 1 and 2 cm 24 of 52 (46%) in the FR group were stone-free compared to 56 of 83 (67%) in the SR group (p < 0.05). For stones with a surface area of 30 to go mm(2) located in the kidney or proximal ureter there was a trend toward an improved SFR in the SR group but differences between the SR and FR groups were not statistically significant. Conclusions: For solitary renal stones between 1 and 2 cm an SR results in a better treatment outcome than an FR for ESWL. However, when stone size is less than 1 cm, SFR differences in the SR and FR treatment groups become less significant.