Syndrome of Inappropriate Anti-Diuretic Hormone Flashcards
(11 cards)
What is the normal function of ADH?
Where is ADH secreted from?
ADH normally stimulates water reabsorption from the collecting duct in the kidneys
Posterior pituitary
What is SIADH?
- SIADH refers to high levels of ADH and high water reabsorption
What does osmolality mean?
What does HIGH urine osmolality mean?
What does LOW urine osmolality mean?
Osmolality = how much solute particles in urine
High urine osmolality = lots of solute per volume of water, i.e concentrated urine
Low urine osmolality = less solute per volume of water, i.e. diluted urine
What are some causes of SIADH?
Ectopic ADH from: small cell lung cancer, pancreatic cancer, prostate cancer
Increased secretion by posterior pituitary
Post-operative major surgery
Neurological: SAH, stroke, encephalitis, meningitis, subdural haemorrhage
Infective: TB, atypical pneumonia, HIV
Drugs: Sulfonylurea, SSRIs, TCAs, cyclophosphamide, Carbamazepine
Other: PEEP, Porphyrias
What are the 3 most common causes of SIADH?
Post-op
SSRIs
Small cell lung cancer
What is the main serum electrolyte finding on U&Es?
Euvolemic hyponatremia
What is the urine findings for SIADH?
High urine osmolality
Low sodium
SIADH is a diagnosis of exclusion - what investigations can you do to help rule in / rule it out?
Must exclude other causes of hyponatraemia e.g:
- adrenal insufficiency
- diuretics
- diarrhoea, vomiting, burns
- excessive water intake
- CKD/AKI
- Heart failure
- liver disease
What is a complication of rapid correction of SIADH?
Symptoms of this?
Central pontine myelinolysis
Spastic quadriparesis, Pseudobulbar palsy (dysarthria, dysphagia, facial motor loss )
Cognitive changes
What is the management of SIADH?
Fluid restriction
ADH receptor antagonists (tolvaptan)
Symptoms of SIADH?
Usually asymptomatic - depends on level of hyponatraemia
Moderate hyponatraemia - headaches, fatigue, muscle aches/cramps, confusion
Severe hyponatraemia - seizures, reduced GCS
