MEASUREMENT of urinary sodium and chloride concentrations is useful whenever
knowledge of whether the kidney is retaining salt will narrow the differential diagnosis. Any
concentration of sodium or chloride in the urine is normal if it favors maintenance of normal
systemic fluid and electrolyte status. Only when a patient's fluid and electrolyte status is
abnormal and one can predict what a normal kidney's protective response would be can
study of the urine electrolytes be of value. Detection of a Salt-Retaining State Urinary sodium …