title: Electrolyte studies. 1. Sodium and water.
abstract: Hyponatremia may be due to relative excess of water or to sodium (Na+) depletion or may be artifactual due to hyperlipemia or excess osmotically active solute in plasma. The cause can be determined from the history, hydration status, and results of simple ancillary tests, eg, osmolality determinations and estimations of urine Na+ concentration. Hypernatremia almost always means water lack. The cause can be determined by correlating clinical findings with urine osmolality test results.
mesh_terms: D006801:Humans; D006955:Hypernatremia / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D007010:Hyponatremia / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D009994:Osmolar Concentration; D013046:Specific Gravity