How is SIADH Diagnosed?
The key to the diagnosis of SIADH is to distinguish it from other causes of dilutional hyponatraemia. The most common causes of a dilutional hyponatraemia are excess infusion of dextrose/saline drips and diuretic administration.
The diagnosis is confirmed by demonstrating the following:
- Hyponatraemia (serum sodium less than 130mmol/L)
- Plasma hypo-osmolality
- Elevated urine osmolality
- The exclusion of adrenal, renal and thyroid dysfunction.