Mechanisms of shockwave action in the human kidney

The effects on the human kidney parenchyma of high-energy shockwaves (HESW) with different energy densities were examined. Kidneys of patients treated by radical nephrectomy for renal cell carcinoma were perfused with cold HTK solution immediately after nephrectomy and kept in hypothermia (8 degrees C) for a maximum of 4 hours. The tumor-free parenchyma was treated with 2000 shocks at energy outputs of 15 kV (16 MPa, 0.15 mJ/mm2), 17 kV (32 MPa, 0.25 mJ/mm2), 19 kV (50 MPa, 0.4 mJ/mm2), and 21 kV (65 MPa, 0.6 mJ/mm2) in an experimental electromagnetic shockwave system (Siemens Co., Erlanger, Germany). Resulting tissue effects were analyzed by histologic and immunohistochemical examinations and confocal laser scanning microscopy. Different sensitivities of cell components, blood vessels, and tubules were found. Laser scanning microscopy revealed nuclear alterations in the vicinity of the focus up to a distance of approximately 10 mm. Severe histologic changes were found in a smaller zone, while immunohistochemistry studies revealed negative collagen IV staining in an area of approximately 4 x 4 mm (all distances measured within the plane perpendicular to the acoustic axis). From these results, it can be concluded that HESW directly damage the tubules and the vascular system, which might explain the clinical changes after extracorporeal shockwave lithotripsy in human patients. The extent of these effects seems to be dependent on the applied energy.