RELATIVE DENSITY OF URINE: METHODS AND CLINICAL SIGNIFICANCE

摘要: The physical properties and chemical composition of urine are highly variable determined in large measure by the quantity type food consumed. specific gravity is ratio density to that water, it dependent on number weight solute particles temperature sample. constituted mainly urea (73%), chloride (5.4%), sodium (5.1%), potassium (2.4%), phosphate (2.0%), uric acid (1.7%), sulfate (1.3%). Nevertheless, osmolality depends only particles. renal production maximally concentrated formation dilute may be reduced two basic elements: (1) generation maintenance a medullary concentration hypertonic plasma (2) mechanism for osmotic equilibration between inner medulla collecting duct fluid. interaction countercurrent system, circulating levels antidiuretic hormone, thirst regulates water metabolism. Renin, aldosterone, prostaglandins, kinins also play role. Clinical estimation concentrating diluting capacity can performed relatively simple provocative tests. However, urinary after taking no fluids 12 h overnight should 1.025 or more, so second morning useful sample screening purposes. Many preservation procedures affect measurements. solids (or water) measured weighing, hydrometer, refractometry, surface tension, osmolality, reagent strip, oscillations capillary tube. These measurements interrelated, not identical. Urinary measurement assess disorders balance discriminate prerenal azotemia acute tubular necrosis. serum concentration, therefore revealed hypo- hypernatremia. disturbances due nonrenal diseases, liver, cardiovascular, intestinal, endocrine, iatrogenic. Fluid management an important topic intensive care medicine. Moreover, usefulness lies interpreting other findings urinalysis, both microscopical.