SIADH

Question 1

Describe the relation between sodium and water in SIADH

Answer 1

hyponatraemia secondary to the dilutional effects of excessive water retention

Question 2

Pathophysiology of SIADH

Answer 2

• excessive ADH release
• water retention
• dilutional hyponatraemia

Question 3

Where is ADH produced and where is it stored?

Answer 3

Produced - hypothalamus
Stored - posterior pituitary

Question 4

Role of ADH

Answer 4

Maintain water balance

=> increases water reabsorption in collecting ducts
=> decreasing the volume of urine produced

Question 5

What cancers can cause SIADH

Answer 5

Lung (small cell)
pancreas
prostate

Question 6

What neurological conditions can cause SIADH

Answer 6

• stroke
• subarachnoid haemorrhage
• subdural haemorrhage
  -meningitis/ encephalitis/ abscess

Question 7

What infections can cause SIADH?

Answer 7

tuberculosis
pneumonia

Question 8

What drugs can cause SIADH?

Answer 8

sulfonylureas
SSRIs
Tricyclics
carbamazepine
vincristine
cyclophosphamide

Question 9

What investigations can help to confirm an SIADH?

Answer 9

Urine osmolality = high

Urine sodium concentration = high

Question 10

Management of ADH

Answer 10

• SLOW correction to avoid central pontine myelinolysis
• fluid restriction
• demeclocycline: reduces responsiveness of the collecting tubule cells to ADH