Diabetes Insipidus Flashcards
What are the 2 types of diabetes insipidus (DI)?
- Central DI
2. Nephrotic DI
What is central DI caused by?
Neurogenic failure in releasing AVP (aka ADH)
Where is the neuronal lesion in central DI? (2)
- Hypothalamus
2. Pituitary gland
What is nephrogenic DI caused by?
Inadequate response to normal and even elevated levels of AVP
What are 3 things nephrogenic DI is associated with?
- Electrolyte abnormalities (low K+ or high Ca2+)
- Renal disease associated with sickle cell anemia
- Various drugs
What are 5 signs/symptoms that is present in both central and nephrotic DI?
- Polyuria
- Polydipsia
- Hypernatremia
- Hypotension
- Shock
How can a physician confirm a DI diagnosis?
Fluid deprivation test
What is a fluid deprivation test?
What does it sound like genius? Google it.
If a patient has DI and is given a fluid deprivation test, what do you expect to see?
You will still see large amounts of dilute urine, even though the body needs to be conserving urine.
If you inject AVP into patients with central DI and nephrogenic DI, which patient will have the greater increase in URINE osmolarity?
Central DI
What is the treatment for central DI?
Desmopressin Acetate (DDAVP), which is an AVP analogue (something that acts like AVP)
Does nephrogenic DI respond to DDAVP treatment? Why?
No, because this illness is resistant to AVP.
How can you treat nephrogenic DI it the patient will be resistant to DDAVP treatment? (2)
- Use a diuretic, because you want to produce natriuresis.
2. Restricting dietary Na+ intake will also help.
What is the high urine flow in DI associated with?
Low rates of solute excretion
What is the difference between osmotic diuresis and DI?
- Osmotic diuresis has a HIGH rate of solute excretion that results in polyuria (a lot of urine).
- DI has a LOW rate of solute excretion that still results in polyuria.
What is happening during chronic renal failure?
Decreasing numbers of healthy nephrons are responsible for excreting the same amount of solutes that a healthy kidney normally excretes.
What are the 3 causes of osmotic diuresis?
- Chronic renal failure
- Diabetes mellitus
- Administration of poorly re-absorbable solutes (ex. mannitol)
What is diabetes mellitus?
Polyuria that occurs when there is too much blood glucose and the kidney is unable to reabsorb it all so it gets excreted. You get polyuria because water follows solute.
What is primary polydipsia?
Psychoneurotic disorder where patients drink a crapload of water.
What is the treatment for primary polydipsia? What is a downside of this?
Drink less water genius!
Downside: limiting water intake can aggravate a patient with DI
