Pulsed irrigation by ejection variable amplifier during and after extracorporeal shock wave lithotripsy and percutaneous lithotripsy : in vitro studies and clinical experience

Discharge of masses of stone fragments after treatment of large stones by extracorporeal shock wave lithotripsy (SWL) or percutaneous lithotripsy may prolong therapy and often necessitates auxilliary procedures. An instrument, the Ejection Variable Amplifier (EVA), was developed for the application of pulsed irrigation of the upper urinary tract that is able to control the pressure in the collecting system by itself. Studies in human cadaver kidneys demonstrated a mean pressure of 14 cm H2O at a flow rate of 80 ml/min. Insertation of a nephrostomy tube lowered the mean pressure to 4 cm H2O. Clinical use of the EVA system in 15 patients produced removal of stone fragments in 13 patients. In two patients treated during SWL, fever occurred. Pulsed irrigation seems to be an effective and noninvasive method for the removal of residual stone fragments. Additional percutaneous surgery may be reduced and the duration of therapy may be shortened by this method.