Park J et al, 2015: Comparison of treatment outcomes according to output voltage during shockwave lithotripsy for ureteral calculi: a prospective randomized multicenter study.
Park J, Kim HW, Hong S, Yang HJ, Chung H
Department of Urology, Eulji University Hospital, Eulji University School of Medicine, Daejeon, Repubic of Korea
PURPOSE: To investigate the effect of fixed versus escalating voltage during SWL on treatment outcomes in patients with ureteral calculi (UC). METHODS: A prospective, randomized, multicenter trial was conducted on 120 patients who were diagnosed with a single adiopaque UC. The patients were randomized into group C (n = 60, constant 13 kV, 3,000 shock wave, 2 Hz) or group E (n = 60, 11.4-12.0-13 kV per 1,000 shock waves, 2 Hz). They were evaluated by plain abdominal radiography and urinalysis at 1 week after a single session of SWL, and repeat SWL was performed if needed. The primary endpoint was stone-free rate at 1 week (SFR1) after SWL. Secondary endpoints were post-SWL visual pain score (VPS), oral analgesic requirements during 1 week, and cumulative SFRs after the second and third sessions of SWL. RESULTS: Groups C and E were well balanced in terms of baseline patients and stone characteristics, including pre-SWL VPS, stone location, and stone size (6.24 ± 1.92 vs. 6.30 ± 2.13 mm). SFR1s were not significantly different between groups C and E (60.0 vs. 68.3 %,
p = 0.447). Analyses stratified by stone size (<6 vs. ≥6 mm) showed no difference in SFR1 (p = 0.148 vs. 0.808). In the analyses stratified by stone location, group E tended to be more effective in distal UC (81.0 vs. 50.0 %, p = 0.052), whereas no difference was seen in proximal UC (p = 0.487). Secondary endpoints were also similar between the two groups.
CONCLUSIONS: Our results suggest that voltage escalation during SWL in UC may not provide superior stone fragmentation compared to fixed voltage.
World J Urol. 2014 Nov 12. [Epub ahead of print]
In contrast to some other studies the authors of this report did not find any significantly improved disintegration of stones by escalating shockwave power during the treatment. It should be noted that most other reports on the positive value of “power ramping” were based on stones in the kidney, not in the ureter. To which extent the shockwave frequency of 120 sw/min (2Hz) influenced the outcome is difficult to know, but the frequency is definitely a factor that needs to be considered.
The conclusion from this report is, however, that there definitely is need for further evaluation of the benefits of “ramping”. Apart from the fact that this treatment strategy facilitates patient adaptation to the treatment the question is: does ramping result in improved disintegration of ureteral stones?