CONGESTION OF THE KIDNEYS. 



367" 



]. According to Traube, the blood-pressure is increased by the 

 retention of a certain quantity of water in the vascular system 

 when the urine is eliminated in small quantity, and by the circu- 

 latory troubles which give rise to the renal alterations ; this eleva- 

 tion of the blood-pressure would lead to compensating cardiac 

 hypertrophy. 2. To this mechanical theory Senator offers in 

 opposition the chemical theory, according to which the increase of 

 the vascular pressure would be due to the retention of urinary 

 waste products in the blood, and mainly of urea. Notwithstand- 

 ing the numerous discussions w^iich have taken place upon this 

 subject, these two hypotheses are still sub judice, and it is very 

 hard to tell which expresses the truth. 



Purulent Nephritis. 



Etiology. The pathogenic agents of purulent nephritis may 

 reach the kidney in two different ways : at times they are conveyed 

 by the blood, at other times they enter it by ascending the ureter. 

 1. In the course of septicemia, of pyemia, endocarditis, pulmonary 

 gangrene, pneumonia, grave pharyngitis, etc., the blood may pro- 

 duce, within the tissue of the kidney, infectious emboli originating 

 from circumscribed inflammatory, purulent, or ichorous centres. 

 (The non-infectious emboli, those originating from a verminous 

 aneurism, for instance, do not produce any purulent phlegmasia, 

 but an ordinary chronic nephritis with infarctus and cicatricial 

 centres.) In the ox purulent nephritis most frequently takes the 

 form of renal abscess. Infectious and septic nephritis are compli- 

 cations which are quite common in cases of dystocia. 2. The 

 phlegmasia, at first limited to the bladder, may, by continuity of 

 tissue, be propagated to the renal pelvis, and thence to the kidney 

 (pyelonephritis). 



Pathological anatomy. In purulent metastatic nephritis we 

 find the renal parenchyma strewn with yellowish-gray spots, from 

 the size of a pin-head to a pea, which represent embolic abscesses 

 which are formed of white corpuscles, softened tissue, and micro- 

 cocci, which are particularly abundant in the centre of the lesion. 

 These abscesses, which seldom acquire large dimensions, are deter- 

 mined by microbic emboli, sometimes a local necrosis, and always 

 have an intense inflammatory reaction in their neighborhood. 



The pyelonephritic abscesses are developed at the expense of 

 purulent tracts which are disposed parallel to the excreting canalS' 



