322 Renal Edema [Dec. 



depend on the nephritis but that both edema and nephritis are the 

 effect of a common cause. Conditions in scarlet fever particularly 

 seem to point to such a relationship, for here signs of edema may 

 precede those of the nephritis and a very marked edema may occur 

 without Symptoms of a kidney lesion. 



Richard Bright early in the nineteenth Century attributed renal 

 edema to a watery condition of the blood, a hydremia, brought 

 about by loss of albumin through the urine. It is now known 

 that in every case of renal edema the albumin content of the blood 

 is diminished and its specific gravity lessened, that is, that the hy- 

 dremia postulated by Bright actually exists. The diluted blood 

 was supposed to pass through the capillaries more readily than the 

 normal blood serum. Later studies have shown this to be improb- 

 able. It was found that not all cases of kidney disease exhibiting 

 albuminuria suffered with edema, and furthermore in conditions 

 where a loss of albumin through other Channels occurred no edema 

 could be detected. Hence hydremia per se, unassociated with other 

 abnormal states, is discredited as the cause of renal edema. 



The dropsy accompanying nephritis might on first thought be 

 considered capable of a simpler interpretation. Since the kidney 

 is the main outlet for the waste fluid of the body, the loss of its 

 power to excrete fluids would result in marked accumulation of 

 water. This retention of water would in the first place dilute the 

 blood, that is produce a " hydremia," and in the second place, wherein 

 this hydremia differs essentially from that brought about by loss 

 of albumin, increase the total volume of the blood and thus result 

 in a condition of plethora. 



The relation of hydremic plethora to edema may be tested ex- 

 perimentally in two ways : Either by diminshing the urinary flow 

 or by increasing the volume of the blood by infusion. 



The effect of diminished urinary flow has been closely observed 

 in animals after ligation of both Ureters and after nephrectomy, and 

 in human beings after the accidental simultaneous closure of both 

 Ureters by urinary calculi or new growths. These subjects continu- 

 ing their normal solid and fluid intake retain all the waste products 

 ordinarily secreted in the urine and yet develop no edema. 



It is possible that not enough fluid is retained in such compara- 



