Electrolytes are involved in most major metabolic functions in the body. Sodium, potassium and chloride are amongst the most important physiological ions and the most often assayed electrolytes. They are supplied primarily through the diet, absorbed in the gastrointestinal tract and excreted by the kidneys.
Chloride is the major extracellular anion and serves to regulate the balance of extracellular fluid distribution.
Serum/plasma: Similarly to the other ions, common causes of decreased chloride include reduced dietary intake, prolonged vomiting, reduced renal reabsorption as well as some forms of acidosis and alkalosis. Increased chloride values are found in dehydration, kidney failure, some forms of acidosis, high dietary or parenteral chloride intake and salicylate poisoning.
Urine: Urinary excretion of chloride normally approximates the dietary intake. Physiological increase of urinary chloride is found with postmenstrual diuresis and a decrease with premenstrual salt and water retention, in parallel with an increase or decrease of urinary sodium levels. Chloride in urine is examined in evaluation of electrolyte composition and in acid-base balance studies.