Energy output modalities of shockwave lithotripsy in the treatment of urinary stones: escalating or fixed voltage? A systematic review and meta-analysis

Purpose To compare the effectiveness and safety of escalating and fixed energy output modalities of shockwave lithotripsy (SWL) in the treatment of urinary stones. Methods A systematic literature search using PubMed, Embase, Cochrane Library and Web of Science was performed to obtain relevant studies up to December 2018. Summarized mean differences (MDs) and risk differences (RDs) with 95% confidence intervals (CIs) were used for comparing continuous and dichotomous variables, respectively. Results Six RCTs including 775 patients were identified. In the overall pooled outcomes, no significant difference was detected between escalating and fixed voltage group regarding initial and final success rate (SR) and stone-free status (SFS), auxiliary procedure and complication (hematoma, febrile episode, and pain) rate. However, when shockwave frequency ≥ 90 shocks/min, total shocks per session ≤ 3000, or 1–3 SWL sessions were performed, escalating group was associated with significantly higher SR1 (defined as SFS + fragments ≤ 4 mm); in addition, escalating group brought significantly less hematoma when total shocks per session ≤ 3000. Conclusions Escalating voltage SWL offered comparable safety and effectiveness to that of fixed voltage SWL. However, escalating voltage SWL could be recommended in following conditions: (1) shockwave frequency ≥ 90 shocks/min, total shocks per session ≤ 3000, or 1–3 SWL sessions, for better stone removal; (2) total shocks per session ≤ 3000, for less hematoma formation.