The Elaboration of Osmotically Concentrated Urine in Renal Disease

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Abstract
The urinary concentrating operation during osmotic diuresis and Pitressin (beta-hypophamine) administration was examined in 25 hydropenic subjects with various renal diseases. The quantity of solute-free water (TmcH2O) reabsorbed in the elab- 2 oration of an osmotically concentrated urine is given by the difference between the osmolar clearance (Cosm) and the urine flow (V). A concentrating operation of considerable magnitude was demonstrated in all subjects with glomerulo-nephritis. In 3 individuals with acute renal failure the TcH2O was so low that a specific damage to the concentrating mechanism has to be assumed. The maximal specific gravity of urine collected after 18 hours of hydropenia had a poor correlation with either TmcH2O or the maximal osmotic U/P ratio.