Diabetes Insipidus Flashcards
What is diabetes insipidus?
Lack of ADH or lack of response to ADH
Prevents kidneys from concentrating urine
What is the presentation of diabetes insipidus?
Polyuria
Polydipsia
Dehydration
Postural hypotension
Hypernatremia
What is the classification of diabetes insipidus?
Nephrogenic
Cranial
What is nephrogenic diabetes insipidus?
Collecting ducts of kidneys do not respond to ADH
What causes nephrogenic DI?
Drugs
Mutations in gene that codes for ADH receptor
Intrinsic kidney disease
Electrolyte disturbance
What is cranial diabetes insipidus?
Hypothalamus does not produce ADH (vasopressin) for the posterior pituitary gland to secrete
What causes cranial DI?
Brain tumours
Head injury
Brain malformations
brain infections
Brain surgery or radiotherapy
What are the investigations for DI?
Low urine osmolarity
High serum osmolarity
Water deprivation test- test of choice
What is the water deprivation test?
Desmopressin stimulation test
1. Fluid deprivation for 8 hours
2. Urine osmolarity measure
3. Synthetic ADH (desmopressin) administered
4. Urine osmolarity measured 8 hours later
What are the results to water deprivation in nephrogenic DI?
Urine osmolarity low before ADH administration and remains low after
What are the results to water deprivation in cranial DI?
Urine osmolarity low before ADH administration
and increases after
What is the management of DI?
Treat underlying cause
Administer desmopressin (synthetic ADH)
- Higher dose and monitoring in nephrogenic DI
