Diabetes Insipidus Flashcards
What is diabetes insipidus?
When your body either doesn’t produce ADH or doesn’t respond to it.
What is the physiology behind ADH (vasopressin)?
- Produced by the hypothalamus
- Secreted by the posterior pituitary gland
- Acts on the collecting ducts of the kidneys, increases their water permeability allowing them to reabsorb water and concentrate the urine
what are the types of diabetes insipidus?
Cranial diabetes insipidus
Nephrogenic diabetes insipidus
Primary polydipsia (not really a type)
what is cranial diabetes insipidus?
when the hypothalamus fails to produced ADH (vasopressin). The kidneys can still respond to it.
What is neophrogenic diabetes insipidus?
When the hypothalamus still produces ADH (vasopressin) but they kidneys cannot respond to it.
What is primary polydipsia?
When you have no problem making or responding to ADH, you just drink too much water and pee excessively.
what causes cranial diabetes insipidus?
Brain tumour trauma radiotherapy meningitis TB encephalitis surgery
What causes nephrogenic diabetes insipidus?
Lithium (used in bipolar)
genetics
any interstitial kidney disease
electrolyte imbalances
what signs are seen in diabetes insipidus?
polyuria polydipsia Hypernatraemia Dehydration Postural hypotension
Decreased urine osmolality (all of the urine solutes have been diluted)
increased serum osmolality (solutes in the blood are concentrated due to losing too much fluid/urine)
What test is done to diagnose and figure out the type of diabetes insipidus?
Water deprivation test/desmopressin test/
What is the water deprivation/desmopressin test?
- Patient doesn’t drink for 8 hours (urine osmolality is measured)
- Patient is given desporessin (synthetic ADH), then urine osmolality is measured again
What results are seen from the water deprivation/desmopressin test in primary polydipsia?
after 8 hours - urine osmolality is high.
No need to carry on with the test and give desmopressin.
what results are seen with nephrogenic diabetes insipidus?
- after 8 hours - urine osmolality low
- after giving desmopressin - urine osmolality is still low (the body doesn’t really react to the synthetic ADH)
What results are seen in cranial diabetes insipidus after the water deprivation/desmopressin test?
- after 8 hours - urine osmolality is low
- after desmopressin - urine osmolality is high (the kidneys respond well to the synthetic ADH and concentrate the urine/reabsorb water at the collecting duct)
what is the treatment?
Cranial - desmopressin
Nephrogenic - Much higher levels of desmopressin and close monitoring
