Acute interstitial lesions of the kidneys, characterized by exudation into the interstitial tissue, of diffuse as well as focal nature, accompanied by, but not dependent upon, degeneration of the epithelium, have been observed commonly in scarlet fever, diphtheria and other infectious diseases. The condition is regarded by some authors as the most frequent pathologic change in the kidneys in scarlet fever.
This form of disease of the kidney is generally accompanied by great enlargement of the organ, which is soft, grayish and opaque on section. In many cases the change occurs in circumscribed areas, located by preference either beneath the capsule, around the glomeruli, or at the bases of the pyramids. The changes above referred to have been previously described as acute interstitial nephritis, productive nephritis, granulating nephritis, and as lymphomatous nephritis. The writings of Councilman have dealt quite extensively with this interesting form of nephritis. In the Reports of