Specimen Name Result Units Range
Plasma Sodium 125 mmol/L (135-145)
Potassium 4.2 mmol/L (3.5-5.5)
Chloride 78 mmol/L (100-109)
Bicarbonate 29 mmol/L (22-32)
Glucose 5.0 mmol/L (3.8-5.5)
Urea 3.0 mmol/L (2.7-7.2)
Creatinine 80 μmol/L (60-110)
Osmolality 270 mmol/kg (275-295)

Thin 80yo male with moderate CAL.

Smoker > 30pkt-years.

Chronic cough, worse recently.
Probable SIADH
  • underlying bronchogenic carcinoma
  • diagnosis requires either urinary Na+/Osmo, or plasma [ADH]

 

Criteria for SIADH

  • Hypo-osmolar Hyponatraemia
  • Urinary [Na+] > 20 mmol/L
  • Urine hypertonic c.f. plasma
  • Normal renal, adrenal, cardiac and hepatic function
  • Absence of drugs causing "SIADH"
    i.e. drug-induced SIADH ≠ true SIADH
  • Corrected by water restriction alone.