Master Of Medicine

Osmolality

All conditions causing hyponatremia are hypo osmolar except

Pseudohyponatremia

• hyperlipidemia
• hypoproteinemia
• Hyperglycemia

ECF volume

Normal in SIADH,Adrenal insufficiency,Hypothyroidism

Increased in Secondary hyperaldosteronism,CHF,Nephrotic syndrome,Cirrhosis

Urine Sodium>20mmol/L

Hypoaldosteronism,saltwasting nephropathy,recent diuretics

SIADH

1. Primary watergain followed by secondary Sodium gain
2. Urine Osmolarity higher
3. Uricosuria- Hypouricemia
4. Euvolemia

Secondary Hyperaldosteronism

Primary sodium gain exceeded by secondary water gain.