| osmolal clearance | The volume of urine that would be excreted per minute if the urinary solutes were accompanied by just enough water to make the urine isosmotic with plasma, i.e., so that the solute excretion did not change the osmolality of body fluids. To calculate it, the volume of urine excreted per minute is multiplied by the urinary osmolality (usually measured by freezing point depression) and divided by the plasma osmolality. Osmolal clearance is less than actual urine flow when urine is hyposmotic and exceeds it when urine is hyperosmotic. (05 Mar 2000) |
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| osmolality | <chemistry> The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per kilogram of solvent. The osmolality is directly proportional to the colligative properties of solutions, osmotic pressure, boiling point elevation, freezing point depression and vapour pressure lowering. (18 Nov 1997) |