THE UBIXABY OBGANS. 617 



DISTURBANCES OF CIRCULATION. 



Anaemia of the kidney occurs in general anaemia : it may be associated 

 with various forms of diffuse nephritis. Local anaemia may be due to 

 thrombosis or embolism. 



Acute Hyperaemia Acute Congestion. This may occur in early phases 

 of an acute inflammatory process or after the ingestion of irritant poisons. 

 The kidneys may be swollen, the vessels distended, and bloody fluid ex- 

 udes from the cut surfaces. There may be extravasation of red blood 

 cells from diapedesis. 



Chronic Hyperaemia Chronic Congestion. This may occur in connec- 

 tion with a similar condition in the other viscera when the circulation is 

 impeded through uncompensated lesions of the heart and lungs, such as 

 chronic endocarditis involving the aortic and mitral valves, cardiac dila- 

 tation, aortic aneurism, emphysema, large accumulations of fluid in the 

 pleural cavities ; or it may be associated with obstruction of the renal 

 vein or inferior vena cava by thrombosis or pressure from tumors, etc. 

 The kidneys in this condition are, when typical, slightly or considerably 

 enlarged, increased in weight, hard, and dark red in color with capsule 

 not adherent and surface smooth. The congestion is most marked in the 

 capillaries of the glomeruli which are widely dilated, often with thickened 

 walls ; in the interlobular veins, the vasa recta, and the stellate veins of 

 the cortical surface. 



The epithelium of the convoluted tubules may be swollen ; or it may be 

 much flattened so that the lumen of the tubule is enlarged. If the con- 

 gestion persist, there is hyperplasia of the interstitial tissue of the kidney 

 with degeneration of the epithelium, the formation of casts, atrophy of 

 the tubules, etc. Chronic congestion may lead to chronic diffuse nephritis. 



Embolism, Thrombosis, and Infarction. If the renal artery or one of its 

 branches be plugged by an embolus or thrombus, an anaemic infarction 

 of the region is the result. There may be one or several such infarctions 

 which are usually more or less wedge-shaped, the apex directed inward 

 corresponding to the vascular territory compromised. They are pale or 

 yellowish, hard, and as inflammatory reaction sets in may be surrounded 

 by a red hyperaemic zone. 



Within the limits of the infarction, necrosis of epithelium or of the 

 entire mass of involved tissue may take place with such subsequent 

 alterations as have been already described on page 76. 



The seat of old and healed infarctions may be indicated by small 

 fibrous cicatrices. ' 



Haeniorrhagic infarctions in the kidney are rare. Infarctions may 

 become the seat of gangrene when putrefactive bacteria gain access to 

 them ; or suppurative inflammation with the formation of abscesses may 

 occur. Embolism of the renal artery may result in necrosis of the entire 



1 For a study 01 the regenerative capacity of the renal epithelium in infarctions see 

 Thorel, Virchow's Arch., Bd. cxlvi., p. 297, 1896, bibliography. Also Thorel, Deutsch. 

 Arch. f. klin. Mod., Bd. Ixxvii., 1903. 



