EDEMA 175 



diminished output of fluid, or of salts, in the urine, during the progress 

 of edema, may be the result of edema rather than its cause. It seems 

 desirable to review the evidence of impaired renal excretory function in 

 various forms of nephritis, particularly in those forms which are associated 

 with edema. Since the changes in the blood are usually assumed to depend 

 on insufficiency of renal excretory function, these changes are considered 

 together with the functional changes in the .kidneys. 



Chronic Interstitial Nephritis. A sharp distinction must be made be- 

 tween the edema occurring in various forms of nephritis, in which edema 

 is the natural result of nephritis, and edema which accompanies heart 

 failure, occurring as a complication of nephritis. By far the greater 

 proportion of cases of chronic nephritis and edema are actually cases in 

 which edema is the result of heart failure, rather than a direct result of 

 nephritis. 



In chronic interstitial nephritis there is the most pronounced evidence 

 of impaired renal function, especially as regards the excretion of such 

 substances as urea, but also of water and salt. Yet edema occurs in chronic 

 interstitial nephritis only as the result of circulatory failure, and the 

 deficiency of renal excretory function cannot be shown to have any direct 

 bearing on its occurrence. For a discussion of renal function and 

 of the changes in the blood in this condition the reader is referred to 

 the section on nephritis in this volume. 



Acute Diffuse Nephritis. In this condition there is direct evidence 

 of disturbed renal function, as shown by the excretion both of urea and 

 of phenolsulphonephthalein. The high salt content of the blood plasma 

 suggests disturbed excretion of salt. Magnus- Alsleben(c), however, has 

 shown that the kidneys in acute nephritis are able, in some cases, to excrete 

 amounts of fluids and of salt far greater than the usual daily output. He 

 gave a patient with acute nephritis a liter of tea to drink and it was 

 practically all retained. The total excretion during the eight hours which 

 followed its administration was only 285 c.c. and sodium chlorid only 0.3 

 per cent. When the same patient was given an intravenous injection of 

 800 c.c. of physiological salt solution, the excretion of urine reached 

 900 c.c. within five hours, and the salt content was 0.6 per cent. Magnus- 

 Alsleben interpreted this result as indicating that in the first instance the 

 fluid was withdrawn from the circulation by the tissues before it had 

 reached the kidneys. He concluded that the kidneys were still able to 

 excrete salt and fluids when they reached the kidneys in sufficiently high 

 concentration. 



The blood in acute nephritis is frequently hydremic, in-&e sense that 

 the protein content is diminished and the specific gravity is lowered, but 

 this condition is not always apparent in the early stages of the disease, 

 when the edema is greatest. The non-protein nitrogen is increased; by 



