Histological examples of injury. Most histologic changes in this study were subtle consisting of mild cell swelling or tissue congestion and varied only slightly from the control tissue (A). Modestly more significant lesions infrequently occurred below the threshold intensity and consisted of some focal congestion and hemorrhage along with individual cell necrosis and tissue compression evident here (B) in a single subcapsular site. Above the threshold, tissue injury was more pronounced. Large, focal pale region (dashed line, C) composed of degenerative epithelial cells surrounded by areas of tubular epithelial cell necrosis with sloughing of tubular lining cells (D). At the extreme, there were distinct foci (dashed line) of liquefactive necrosis or emulsification (E) that on higher magnification (F) abruptly interfaced with more normal tissue and resulted in cavities which were filled with lysed and intact erythrocytes (hemorrhage).