Diagnostic Values

SIADH

CSW

Serum Na level, mEq/L [11]

Hyponatremia (<135)

Hyponatremia (<135)

Serum Osmolality, mOsm/kg [26]

<275 (low)

<275 (low)

Urinary Na level, mEq/L [26]

Normal or elevated (>30)

Elevated (>30)

Urinary Osmolality, mOsm/kg [26]

Elevated (>100)

Elevated (>100)

Urinary Specific Gravity [18]

>1.010 (concentrated)

>1.010 (concentrated)

Urine Output [18]

Decreased (500 mL/24 h)

Decreased

Fluid Volume Status [13]

Euvolemic

Hypovolemic

Central Venous Pressure [2] [26]

Normal, or increased (>6 cm water)

Decreased (<6 cm water)

Fractional Excretion

Of Uric Acid [14] [26]

>12%, then decreases as Na returns to baseline

>12%, and stays elevated as Na returns to baseline

Fractional Excretion of

Phosphate [32]

Normal (<10%)

Elevated (>20%)