Specimen Name Result Units Range
Plasma Sodium 122 mmol/L (135-145)
Potassium 4.4 mmol/L (3.5-5.5)
Chloride 94 mmol/L (100-109)
Bicarbonate 22 mmol/L (22-32)
Anion Gap 11 mmol/L (7-17)
Glucose 7.6 mmol/L (3.8-5.5)
Urea 3.5 mmol/L (2.7-7.2)
Creatinine 60 μmol/L (60-110)
Urine Sodium 60 mmol/L (> 20)
Osmolality 531 mmol/kg

64yo with moderate CAL.

Smoker > 35pkt-years.

General malaise, worsening cough.
Probable SIADH
  • SIADH 2° to bronchogenic carcinoma

 

Aetiology SIADH

  1. Malignancies → autonomous ADH release
    • lung, pancreas, sarcomas, Hodgkin's, thymoma
  2. Non-malignant pulmonary disease
    • TB
    • lung abscess, empyema
    • pneumonia, viral pneumonitis
    • CAL
  3. CNS disease
    • trauma - CHI, fractures
    • vascular accidents - SAH, SDH, thrombosis
    • infections - encephalitis, meningitis (TB, bacterial)
    • GBS, SLE, AIP
  4. Miscellaneous - IPPV, hypothyroidism, ? hypoadrenalism

Drug-Induced 'SIADH'

  • TCA's
  • chlopropamide, carbamazepine, clofibrate
  • cyclophosphamide, vincristine, vinblastine
  • GA's, opioids
  • oxytocics

Diagnostic Criteria SIADH

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