[Does SWL for ureteral stone with less than 60 shock waves per minute improve treatment results?]

Extracorporeal shock wave lithotripsy (SWL) is a wide spread option for the treatment of the upper urinary tract urolithiasis. EAU guideline recommends the treatment with 60-90 shots per minute for the optimal frequency of SWL, but there is no report on the efficiency of SWL with the frequency less than 60 shots per minute.

To determine the optimal shock wave frequency of SWL, we prospectively randomized total 247 patients with ureteral stone to the four different treatment groups: group A (76 pts.), group B (68 pts.), group C (55 pts.) and group D (48 pts.). These groups were treated with the frequencies of 80, 60, 45 and 30 shots per minute respectively using Dornier Lithotripter D. One treatment took forty minutes, resulting in the total shock waves per session of 3,200, 2,400, 1,800 and 1,200 for group A, B, C and D, respectively.

The total numbers of the SWL sessions were statistically not different among the four groups. Importantly, there was statistically no difference among the four groups about the stone clearance rates and the stone reduction efficiencies on the next day, after one week and after one month of the treatment. In addition, only two additional ureteral stenting for pyelonephritis and one renal subcapsular hematoma were observed.

This study suggests that the efficiency of SWL with the frequency of 30 or 45 shots per minute is similar to that of 60 or 80 shots for stone reduction and clearance.