Histological and ultrastructural changes in rat kidney after cryosurgery.

Effect of cryoinjury to normal rat kidney was studied at the light and electron microscope level, and characterization of the time course of pathologic changes in kidney tissue after cryosurgery was described from 1 hr up to 14 days after production of a standard cryolesion. Cryoinjury to the kidney resulted in sharply demarcated lesions with minimal inflammatory response during the period of cell destruction and healing by fibrosis. Cellular protein was completely coagulated within 1 hr after cryoinjury, with crystallization of protein and disruption of membranes. Cellular disruption was rapid, and the clearance of cellular debris from the area of injury by macrophage infiltration was accomplished through a quite mild inflammatory reaction. Supporting stromal elements of renal parenchyma remained intact, including collagen tubular framework and basement membranes, and formed the lattice over which fibrosis developed.