Diabetes Insipidus Flashcards
What causes diabetes insipidus?
Lack of ADH/ lack of a response to ADH
What causes diabetes insipidus?
Lack of ADH/ lack of a response to ADH.
What are the two causes of diabetes insipidus?
Nephrogenic/ cranial
What is primary polydipsia?
Normal ADH system but patient drinks too much water leading to excessive urine production.
What is nephrogenic diabetes insipidus?
Kidneys do not respond to ADH.
What are the causes of nephrogenic diabetes insipidus?
Lithium use
Mutations to ADH receptor gene
Intrinsic kidney disease
Hypokalaemia and hypercalcaemia
What are the causes of cranial diabetes insipidus?
Brain tumours
Head injury
Brain malformations
Brain infections
Surgery
Radiotherapy
What is cranial diabetes insipidus?
Hypothalamus does not produce enough ADH
Presentation of diabetes insipidus?
Polyuria
Polydipsia
Dehydration
Postural hypotension
Hypernatraemia
Investigations in suspected diabetes insipidus?
Water deprivation test
What is a water deprivation test?
- Avoid fluids for 8 hours
- Measure urine osmolarity
- Give synthetic ADH –> desmopressin
- Measure urine osmolarity again
What is the result of the water deprivation test in cranial diabetes insipidus?
Urine osmolarity is high
What is the result of the water deprivation test in nephrogenic diabetes insipidus?
Urine osmolarity is low
What is the result of the water deprivation test in primary polydipsia?
Urine osmolarity is high before and after test
Management of diabetes insipidus?
Desmopressin in cranial diabetes
Desmopressin in higher doses in nephrogenic diabetes (with close monitoring)
