Osmotic Pressure of Plasma Proteins in Nephritis. ∗

Abstract

We have determined the osmotic pressure of the plasma colloids in normal persons and in cases of glomerulonephritis with and without edema, using the method of Schade 1 for the determination of the osmotic pressure of the plasma proteins at 37°C. against a collodion membrane. The normal values for the osmotic pressure of the plasma proteins were from 20 to 23 mm. Hg. The osmotic pressure of the plasma proteins was 11 mm. Hg. or lower in all our cases of nephropathic edema investigated up to the present time. Edema was not observed in cases of nephritis where the osmotic pressure of the colloids of the plasma was 17 mm. Hg. or above. Undoubtedly lowering of the osmotic pressure of the plasma proteins is a factor in the formation of edema in nephritis and nephrosis. It is best thought of as determining a “tendency to edema formation.” Other factors as ability of the kidneys to excrete water, salt retention, anoxemia and toxins altering capillary permeability, etc., contribute to the formation of edema. By reducing water intake it was possible to reduce the extent of the edema in some cases with low osmotic pressure of the plasma proteins. We are now attempting to determine experimentally the level of osmotic pressure of the plasma proteins below which edema must form even with good renal function and no salt retention. When the osmotic pressure of the plasma proteins is below the hydrostatic pressure at the venous end of the capillary system, undoubtedly edema must form because water can not stay in the capillaries.