Table 3: Diagnostic considerations for syndrome of inappropriate antidiuretic hormone.

Decreased effective osmolality of the extra-cellular fluid Plasma osmolality <275 mOsmol/kg H20

Inappropriate urinary concentration Urine osmolality >100 mOsmol/kg H20 with normal renal function

Clinical euvolemia No signs of hypovolemia or hypervolemia on clinical examination

Elevated urinary sodium excretion despite normal sodium and water intake

No other potential causes of euvolemic hypoosmolality No hypothyroidism, hypocortisolism or diuretic use