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CHRONIC INTERSTITIAL NEPHRITIS. 411 



On section, the cortex is found to be two or three times 

 its normal thickness, its mottled appearance being due to 

 patches of fatty degeneration in the tubular epithelium. 



The microscopical lesions are the same as in acute parenchy- 

 matous nephritis, only more marked. The most prominent 

 feature is the degenerative changes in the epithelium of the 

 convoluted tubules ; the epithelial cells are swollen, granular, 

 and many are in an advanced stage of fatty degeneration, 

 finally breaking down completely, and filling the lumen of the 

 tubule with a granular and fatty debris, the lining epithelium 

 being entirely destroyed. Within the tubules may be also 

 hyaline, granular, and fatty casts. There is generally some 

 increase in the intertubular connective tissue. The changes 

 in the glomeruli are equally marked, increased thickness of 

 Bowman's capsule and of the connective tissue between the 

 capillaries tending to convert them into atrophied fibrous 

 bodies. 



In chronic interstitial nephritis the kidney is usually greatly 

 reduced in size to less than two ounces in extreme cases and 

 is remarkably tough in consistency ; its surface is of a reddish- 

 gray tint, and uneven from the presence of small nodules or 

 granulations, fairly regular in size about that of a millet- 

 seed. The capsule is thickened, opaque, and firmly adherent. 



On section , the most noticeable feature is the marked atrophy 

 of the cortex, appearing as a narrow rim but a few millimetres 

 in thickness. The pyramids are also reduced in size, the 

 atrophy of the intervening glandular tissue giving them the 

 appearance of being closely packed together. 



Microscopically, the prominent features are the atrophy of 

 the glomeruli and uriniferous tubules, the tubular epithelium 

 having undergone granular and fatty degeneration ; and great 

 increase in the connective-tissue stroma. The majority of 

 glomeruli have become dense and fibrous nodules, but one- 

 half their normal size. Here and there may be well-preserved 

 tubules and glomeruli. Occasionally tubules are met which 

 seem to have undergone a sort of complementary dilatation, 

 as the result of obliteration of tubules in other areas, becom- 

 ing so exaggerated in some instances as to form cysts, large 

 enough to be seen with the naked eye. Sometimes these 

 cysts occur in rows, suggesting their origin from a single 



