Ultraslow full-power shock wave lithotripsy versus slow power-ramping shock wave lithotripsy in stones with high attenuation value: A randomized comparative study

Abstract

Objectives: To compare the efficacy and safety of ultraslow full-power versus slow rate, power-ramping shock wave lithotripsy in the management of stones with a high attenuation value.

Methods: This was a randomized comparative study enrolling patients with single high attenuation value (≥1000 Hounsfield unit) stones (≤3 cm) between September 2015 and May 2018. Patients with skin-to-stone distance >11 cm or body mass index >30 kg/m² were excluded. Electrohydraulic shock wave lithotripsy was carried out at rate of 30 shock waves/min for group A versus 60 shock waves/min for group B. In group A, power ramping was from 6 to 18 kV for 100 shock waves, then a safety pause for 2 min, followed by ramping 18-22 kV for 100 shock waves, then a safety pause for 2 min. This full power (22 kV) was maintained until the end of the session. In group B, power ramping was carried out with an increase of 4 kV each 500 shock waves, then maintained on 22 kV in the last 1000-1500 shock waves. Follow up was carried out up to 3 months after the last session. Perioperative data were compared, including the stone free rate (as a primary outcome) and complications (secondary outcome). Predicting factors for success were analyzed using logistic regression.

Results: A total of 100 patients in group A and 96 patients in group B were included. The stone-free rate was significantly higher in group A (76% vs 38.5%; P < 0.001). Both groups were comparable in complication rates (20% vs 19.8%; P = 0.971). The stone-free rate remained significantly higher in group A in logistic regression analysis (odds ratio 24.011, 95% confidence interval 8.29-69.54; P < 0.001).

Conclusions: Ultraslow full-power shock wave lithotripsy for high attenuation value stones is associated with an improved stone-free rate without affecting safety. Further validation studies are required using other shock wave lithotripsy machines.

Keywords: Hounsfield unit; ramping; slow shock wave lithotripsy; stone attenuation value; ultraslow shock wave lithotripsy.