Increased damage to stones without increased damage to cells with a dual-reflector lithotripter

Extracorporeal shock wave lithotripsy (ESWL) is a commonly used clinical treatment to comminute kidney stones into tiny fragments that can be expelled through a patient's urinary tract. Cavitation, the violent growth and collapse of microscopic bubbles, may be an important mechanism in both stone fragmentation and renal tissue damage during ESWL. In water, a conventional lithotripter generates a cavitation field in a cylindrical volume, /spl sim/1 cm wide/spl times/10 cm long. A dual-reflector lithotripter, consisting of two identical spark-gap lithotripters facing each other and firing simultaneously, creates a more localized cavitation field, /spl sim/3 cm wide/spl times/5 cm long. Stone breakage at the focus, and hemolysis, 2-cm from the focus, were assessed using both conventional lithotripsy (CL) and dual-reflector lithotripsy (DRL). Following exposure to 100 shots of DRL, the number of stone fragments >1.5 mm were 17.3/spl plusmn/3.9 at 18 kV, 5.3/spl plusmn/2.8 at 15 kV and 3/spl plusmn/1.7 at 12 kV. Following exposure to 200 shots of CL, the number of stone fragments >1.5 mm were 3.5/spl plusmn/1.9 at 18 kV, 1.6/spl plusmn/0.8 and at 15 kV, and 1.7/spl plusmn/1.1 at 12 kV. Following exposure to 100 shots of DRL, values for hemolysis were 8.1/spl plusmn/2.3% at 18 kV and 4.9/spl plusmn/1.1% at 15 kV. Following exposure to 200 shots of CL, values for hemolysis were 10.9/spl plusmn/3.4% at 18 kV and 7.8/spl plusmn/2.5% at 15 kV. These data demonstrate that, in vitro, DRL results in enhanced stone comminution at the focus and decreased damage to red blood cells a short distance from the focus.