Ito K. et al., 2020: Extremely-slow, half-number shockwave lithotripsy for asymptomatic renal stones
Ito K, Takahashi T, Kanno T, Okada T, Higashi Y, Yamada H.
Department of Urology, Ijinkai Takeda General Hospital, Kyoto, Japan.
Purpose: To compare the treatment success rate and safety of reduced (30 shocks/min, 1,200 shocks/session) versus standard (60 shocks/min, 2,400 shocks/session) extracorporeal shockwave lithotripsy for the management of renal stones.
Materials and methods: We retrospectively analyzed 404 patients who underwent extracorporeal shockwave lithotripsy for 5-20-mm renal stones between April 2011 and March 2019. Patients selected the reduced or standard protocol (group R and S) after explaining the potential benefits and disadvantages. The primary outcome was treatment success within 12 weeks, which was defined as no residual fragment or fragments <4 mm on ultrasonography and plain radiograph.
Results: In total, 94 and 310 patients underwent shockwave lithotripsy with a reduced and standard protocol, respectively. The background characteristics of the participants did not significantly differ. The treatment success within 12 weeks was achieved in 78 (83.0%) patients in group R and 259 (83.5%) in group S (p=0.88). The median number of the session was 3 (interquartile range, 2-4) in both groups (p=0.53). The total complication rates were 5.4% in group R and 6.1% in group S. Three (1.0%) patients in group S experienced perirenal hematoma, which was conservatively treated. The reduced protocol was not associated with treatment success in the multivariate analysis adjusted for potential confounders (odds ratio, 0.91; 95% confidence interval, 0.46-1.80; p=0.78).
Conclusions: The new treatment amendment with a slower delivery rate successfully reduced the total number of shocks need to fragment renal stones <20 mm without compromising the stone-free rate.
Investig Clin Urol. 2020 Dec 3. doi: 10.4111/icu.20200285. Online ahead of print. PMID: 33314807. FREE ARTICLE
This report is highly interesting because over the years there has been a continuous debate on the optimal frequency of shockwave administration. In this article the authors showed, in a non-randomized study, that 1200 shockwaves at 0.5 Hz (30 sw/min) resulted in identical results compared with those recorded in patients treated with 2400 shockwaves at 1.0 Hz (60 sw/min). All patients were treated with Dornier Delta II or Gemini.
Although neither univariate nor multivariate analysis disclosed any difference between the two treatment strategies, it might be more comfortable for the patient with the lower frequency. But that experience might differ from one patient to another and I have met several patients who found it better with high frequency at 1.5 Hz than low frequency at 1.0 Hz, because a longer interval between successive shockwaves can be uncomfortable. Nevertheless, it seems reasonable to assume that a low frequency means a more gentle procedure. Moreover, the physical effects of shockwaves speak in favour of low-frequency treatment.
The possibility to deliver shockwaves at a rate of 0.5 Hz is not commonly available in most lithotripters. The authors circumvented this problem by using a virtual ECG device set at 30 beats per minute. My recommendation to manufacturers of lithotripters is to add a function that allows variable administration of shockwaves below 1 Hz.