AN IMPROVED CONCENTRATION TEST OF RENAL FUNCTION

Abstract

In a previous paper,¹the value of the specific gravity of the urine as a test of kidney function was discussed. It was pointed out that if the specific gravity of the urine is to be employed as a functional test, certain conditions must be fulfilled: First, a sufficient amount of solid wastes must be presented to the kidneys for excretion. This was obtained by a special diet. Second, the amount of water available for the excretion of these wastes must be limited. This condition was observed by restricting the fluid intake. The purpose of these conditions was to impose maximal strain on the kidneys and to secure the most concentrated urine possible. Under these conditions it was found that normal individuals were able to concentrate the urine to a specific gravity of 1.026 or above. Diseased kidneys were unable to concentrate to 1.026. The more severe the renal