Flashcards in Lecture 25: Diabetes Insipidus Case Deck (71)
How do patients with primary polydipsia respond to the formal water deprivation test?
Their urine concentrate a little (but not until 1000 mosm/kg like in normal people) and they do not respond to AVP
How else can we differentiate central DI from nephrogenic DI? When is this usually done?
Measure plasma AVP when blood is hyperosmolar (dehydrated)
Usually done after a formal water deprivation test
Explain how hyperosmolarity affect the brain. Why do we have to be very careful when fixing hyperosmolar patients?
High osmolality = shrinking of the brain = brain adapts by accumulating electrolytes and organic osmolytes
If you fix it too rapidly it will cause cerebral edema
When do patients with DI experience symptoms of hyperosmolarity and hypovolemia?
When they cannot drink in response to thirst
Why do people with DI prefer cold water?
Cold water better quenches thirst
Would you ever confuse a DI patient with an osmoreceptor dysfunction patient?
NOPE because the osmoreceptor dysfunction patient has no thirst
What does wanting COLD water mean?
Means someone has TRUE thirst
Is diabetes insipidus associated with obesity?
What blood cells line the collecting duct cells?
How can central DI be confirmed with a biopsy?
Post pit will show T-cells which means it's idiopathic central DI