Response of mouse kidney to hyperthermia: pathology and temperature--dependence of injury.

Hyperthermia either alone or in combination with radiotherapy and chemotherapy is being used increasingly in the treatment of malignant tumors. This study was designed to evaluate the response of the mouse kidney exposed to a range of hyperthermic temperatures (41 to 45 degrees C) used to induce regression of malignant tumors. Minimal histologic evidence of renal injury occurred in the proximal tubules of the subcapsular region. More extensive damage was characterized by necrosis of tubules and glomeruli in a sharply circumscribed area that involved the lateral subcapsular area where the temperature induced was highest. The tissue histologic reaction was maximal by 24 hours. At temperatures below 41 degrees C no necrosis occurred, whereas at temperatures between 42 and 45 degrees C there was an increasing incidence of necrosis. This increase in tissue reaction above 42 to 43 degrees C is consistent with reported observations from tissue culture and in vivo skin heating experiments, and indicates that normal tissue injury may occur in the same range of temperatures shown to cause regression in malignant tumors.