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Chloride is the major anion of the extracellular fluid. Its precise function in the body is not well understood, but it is involved in maintaining osmotic pressure, hydration, and ionic neutrality. The concentration in serum or plasma is measured with an ion selective electrode. Hyperchloremia may occur with excessive loss of bicarbonate due to diarrhea, renal tubular acidosis, mineralocorticoid deficiency, compensated respiratory alkalosis, and excessive dietary intake. Hyperchloremia frequently accompanies hypernatremia. Mild elevations may be seen in primary hyperparathyroidism. Hypochloremia may result from: loss of hydrochloric acid from vomiting , excessive mineralcorticoid production, and salt losing renal disease such as pyelonephritis. Low serum chloride levels are also seen in conditions associated with high serum bicarbonate concentrations such as compensated respiratory acidosis or metabolic alkalosis. Chloride measurements are useful when interpreting difficult acid base disorders. Hyperchloremia often indicates acidosis (primary or compensatory), whereas hypochloremia indicates primary or compensatory alkalosis. Reference range is 98 - 107 mEq/L. Specimen requirement is one SST or green top (heparin) tube of blood. Chloride, Urine Measurement of urinary chloride is most useful in the differential diagnosis of persistent metabolic alkalosis. Metabolic alkalosis can be classified as chloride responsive or resistant. Chloride responsive alkalosis is due to loss of hydrogen ion and chloride containing extracellular fluid, such as occurs with vomiting, nasogastric suction, and diuretic therapy. Chloride resistant alkalosis results from excessive secretion of mineralcorticoid hormones, which causes bicarbonate reabsorption. The most common causes are hyperaldosteronism, Cushing's Syndrome, exogenous steroid administration, licorice ingestion and alkali ingestion.
The reference range for a 24 hour urine collection is 110 - 250 mEq/24 hours. A 24 hour urine specimen should be collected in a container without preservative. |
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