110 THE URINARY ORGANS. 
What are the causes of, and what changes occur in, suppurative 
nephritis ? 
The inflammation may be started by injury, bacterial emboli, or may 
arise from undiscoverable causes. The inflammatory process is an 
exudative one. The whole kidney may be converted into a mass of 
pus, blood and broken-down tissue, or there may be a formation of 
circumscribed abscesses. When caused by infectious emboli the kidney 
may be dotted with little white points surrounded by a red zone. 
Micrococci may often be found. In some cases the whole kidney 
may be so changed that it is nothing but a sac filled with pus. 
What are the changes in pyelo-nephritis ? 
The mucous membrane of the pelvis is congested, thickened, and 
there may be patches of fibrin upon its surface. The renal epithelium 
is swollen and degenerated. Abscesses and collections of pus may be 
scattered through the kidney and there may be an exudation of pus- 
cells between the uriniferous tubules. 
What are the lesions in chronic pyelo-nephritis ? 
The mucots membrane lining the pelvis and calices of the kidney, 
and the epithelium covering the diseased surfaces may be changed and 
little polypoid growths be formed. There may be a layer of granulation 
tissue formed beneath the epithelial layer. The mucous membrane 
may be covered with pus and fibrin, or the pelvis of the kidney may 
be filled with pus. There is a marked increase in the amount of con- 
nective tissue in the kidney. Pus may also be present in the kidnev 
itself, : 
Describe tubercular inflammation of the kidney. 
The inflammatory process is the same as in tubercular inflammation 
elsewhere. It may occur ina kidney already the seat of a chronic 
diffuse nephritis, or the nephritis may be added to the tubercular 
inflammation. 
What are the causes of, and changes found with, hydronephrosis ? 
This condition is produced by an obstruction to the flow of urine 
from the pelvis of the kidney, and may be congenital or mechanical. 
The kidney tissue is flattened out by the pressure of the retained 
urine. It may remain normal or may be the seat of a suppurative 
nephritis or of a chronic diffuse nephritis. 
What can be said of cysts of the kidney ? 
These cysts may be congenital, and seem to be formed by dilatation 
