Urinary electrolytes

Urinary electrolytes can be a useful tool in the Emergency Department. For those patients with volume depletion, acute oliguria and hyponatremia, the determination of urinary sodium levels can aid in diagnosing the etiology of the presenting condition. Urinary potassium levels can aid the clinician in determining the cause of the potassium loss, either renal or extrarenal. For those patients with metabolic alkalosis, determination of the urinary chloride levels will allow the physician to determine if the alkalosis is chloride responsive or chloride resistant. It must be kept in mind that the measurement of any urinary electrolyte is relatively valueless unless it is interpreted with other data and/or observation of the patient. It should be noted also that a solitary value may not be adequate for making a diagnosis, and serial urinary electrolyte value assessment may be necessary. In the critically ill patient, it may be prudent to obtain a urine sample before the administration of a diuretic, the administration of potassium, or large amounts of saline. This procedure will allow for a more accurate assessment of the patient's pretreatment status.