Diabetes Insipidus Flashcards
(12 cards)
What is diabetes insipidus?
Polydipsia and polyuria due to either:
ADH deficiency due to defective hypothalamus (cranial diabetes insipidus)
Lack of collecting ducts in kidney response to ADH (nephrogenic diabetes insipidus)
Where is ADH produced and released from?
Produced in hypothalamus
Released by posterior pituitary gland
Causes of nephrogenic diabetes insipidus?
Lithium
Genetic mutations in ADH receptor gene (X linked)
Hypercalcaemia
Hypokalaemia
Kidney diseases
Causes of cranial diabetes insipidus?
Idiopathic
Brain tumours
Brain surgery
Brain injury
Brain inflammation
Genetic mutation in ADH gene (Autosomal dominant)
Wolfram syndrome
What is Wolfram syndrome
Genetic condition causing optic atrophy, deafness, and diabetes mellitus
Symptoms of diabetes insipidus?
Polyuria (>3L/day)
Polydipsia
Dehydration
Postural hypotension
Investigations?
Urine osmolality - low
Serum osmolality - high/normal
depending whether urine loss balanced by water intake
24 hour urine collection - >3L
Water deprivation test
What is the water deprivation test also known as
Desmopressin stimulation test
What would primary polydipsia show on water deprivation test?
Urine osmolality after deprivation - high
No desmopressin required
What would cranial diabetes insipidus show on water deprivation test?
Urine osmolality after deprivation - low
After desmopressin - high
What would nephrogenic diabetes insipidus show?
Urine osmolality after deprivation - low
After desmopressin - low
Management of Diabetes Inspidus
Cranial: desmopressin. Manage Na+ as risk of hyponatraemia
Nephrogenic: ensure access to water, high dose desmopressin, thiazides diuretics, NSAIDs
