Test Details: Sodium is the primary extracellular cation. Sodium is responsible for almost one-half the osmolality of the plasma and, therefore, plays a central role in maintaining the normal distribution of water and the osmotic pressure in the extracellular fluid compartment. The amount of sodium in the body is a reflection of the balance between sodium intake and output. Hyponatremia (low sodium) is seen is condtions such as decreased sodium intake, precipitated by conditions like vomiting, diarrhoea, many other clinical conditions like nephrotic syndrome, primary and secondary adrenocortical insufficiency and congestive heart failure. Hypernatremia (high sodium) is seen in liver disease, cardiac failure, burns, osmotic diuresis. Other causes include decreased production of antidiuretic hormone diabetes insipidus, inappropriate forms of parenteral therapy with saline solutions, or high salt intake without corresponding intake of water, Cushing syndrome, diabetic acidosis, etc.