The Use of Diuretics in Bright’s Disease
Diuretics are substances which increase the volume of the urine by some modification of the complicated process by which urine is formed. Part of this process takes place outside the kidney, beginning with the absorption of fluid from the alimentary canal, and various metabolic processes take place in the tissues before urine is actually elaborated in the kidney. Diuretics, therefore, may be renal or extrarenal in their action. The mode of action and the site of action, in the case of most diuretics, is at best uncertain and may occur at various points in the tissues or tissue fluids, in the capillary walls or blood itself, in the general circulation or renal circulation, as well as in the renal tubules and glomeruli.
The generally accepted modern theory of renal secretion as formulated by Cushny offers a basis for a classification of diuretic agents which Solis-Cohen1 suggested. According to this theory, there occurs a simple diffusion through the glomerular tufts of all the diffusible substances contained in the blood, the same proportion and concentration being retained. This filtrate then passes into the tubules where there is a resorption of most of the water and all or a great part of certain of the dissolved constituents of this glomerular filtrate. The residue of water, together with those dissolved substances which are not reabsorbed, constitute the urine. The reabsorbed substances are known as threshold substances, inasmuch as they appear in the excreted urine only when their concentration in the blood and hence in. . .