Extracorporeal shock wave lithotripsy (ESWL) remains the recommended first line treatment for stones <2cm in the renal pelvis and upper or mid-pole calyces (Türk C, Knoll T, Petrik A, et al. European Association of Urology Guidelines on Urolithiasis. 2014). There are a number of associated risks with lithotripsy including renal haematoma. In this prospective randomised study, the investigations seek to establish if stepwise voltage ramping protects the kidney from damage during ESWL. The study included patients with solitary or multiple unilateral radiopaque kidney stones <3 cm diameter. Exclusion criteria included concurrent ureteric stones and contraindications to ESWL. Four hundred and eighteen patients were randomised to receive either stepwise voltage ramping (500SWs at 14kV, 1000SWs at 16kV and 1000kVs at 18kV) or fixed maximal voltage (2500SWs at 18kV). Primary outcome was evidence of renal haematoma on ultrasound scan 24 hours following ESWL. Secondary outcomes were urinary β2-microglobulin and microalbumin at 24 hours (as markers for renal damage), stone disintegration and stone free rates at three months, number of secondary interventions required and complication rates. The study identified significantly fewer renal haematomas in the stepwise voltage ramping group (5.6% vs. 13% in the fixed group). β2-microglobulin levels were higher at 24 hours in the fixed maximal voltage group. There was no significant difference in the level of urinary microalbumin, stone disintegration, stone free rates, rate of secondary intervention and complications other than haematoma. What remains unclear is the clinical significance of the renal haematomas identified. None of the patients required blood transfusions and all remained haemodynamically stable. Nonetheless, the lower rate of haematomas in the stepwise voltage group did not result in a compromise in treatment effectiveness. It is notable in this study that ESWL was performed using either regional or general anaesthesia, which is not commonplace in the UK and may preclude the study results being generalised into UK practice.
Stepwise voltage ramping causes less renal haematomas than fixed maximal voltage ESWL
Reviewed by Sophia Cashman
Does stepwise voltage ramping protect the kidney from injury during extracorporeal shockwave lithotripsy? Results of a prospective randomized trial.
