A NEW PIEZOELECTRIC POWER SOURCE AND FIRST ANIMAL-EXPERIMENTS

The disintegration efficacy of a new piezolectric power source has bee n measured in vitro using a standard plaster model stone. Shock wave p ressure profiles were determined in the focal area by a PVDF-membrane hydrophone. Compared to the standard piezoelectric source the disinteg ration efficacy has been improved by about 50%. 11 beagle dogs with 21 renal units were treated with 2000 shocks in a single session at the highest energy level by focusing the renal pelvis. Histopathological e xaminations were performed in 7 kidneys immediately after shock wave a pplication, in 7 kidneys 6 weeks and in 7 kidneys 12 weeks after. Simu ltaneously CT-examinations and angiographies were performed. CT-findin gs and angiographies showed circumscribed intrarenal hematoma, periren al edema but no larger perirenal injuries immediately after treatment. Corresponding to these findings histopathologically different early r enal alterations were found like hematopyelon, intrarenal and subcapsu lar hematoma, papillary necroses, and vascular lesions. Despite the si gnificant damage immediately after application of shock waves, only su btle alterations were observed 6 and 12 weeks after treatment: all kid neys showed small cordlike superficial and intrarenal scars along the pathway of the shock wave, only 1 of 14 kidneys showed a necrosis of t he papillary apex. No vascular lesions could be found 6 and 12 weeks a fter treatment. With respect to further examinations the new generator with an improved efficacy of disintegration seems not to leave seriou s and permanent damage renal parenchyma. In comparison to the to the e xperimental data collected by the standard piezogenerator comparable r esults have been achieved with the new power source.