Diabetes Insipidus

Question 1

What are the 2 types of diabetes insipidus (DI)?

Answer 1

1. Central DI

2. Nephrotic DI

Question 2

What is central DI caused by?

Answer 2

Neurogenic failure in releasing AVP (aka ADH)

Question 3

Where is the neuronal lesion in central DI? (2)

Answer 3

1. Hypothalamus

2. Pituitary gland

Question 4

What is nephrogenic DI caused by?

Answer 4

Inadequate response to normal and even elevated levels of AVP

Question 5

What are 3 things nephrogenic DI is associated with?

Answer 5

1. Electrolyte abnormalities (low K+ or high Ca2+)
2. Renal disease associated with sickle cell anemia
3. Various drugs

Question 6

What are 5 signs/symptoms that is present in both central and nephrotic DI?

Answer 6

1. Polyuria
2. Polydipsia
3. Hypernatremia
4. Hypotension
5. Shock

Question 7

How can a physician confirm a DI diagnosis?

Answer 7

Fluid deprivation test

Question 8

What is a fluid deprivation test?

Answer 8

What does it sound like genius? Google it.

Question 9

If a patient has DI and is given a fluid deprivation test, what do you expect to see?

Answer 9

You will still see large amounts of dilute urine, even though the body needs to be conserving urine.

Question 10

If you inject AVP into patients with central DI and nephrogenic DI, which patient will have the greater increase in URINE osmolarity?

Answer 10

Central DI

Question 11

What is the treatment for central DI?

Answer 11

Desmopressin Acetate (DDAVP), which is an AVP analogue (something that acts like AVP)

Question 12

Does nephrogenic DI respond to DDAVP treatment? Why?

Answer 12

No, because this illness is resistant to AVP.

Question 13

How can you treat nephrogenic DI it the patient will be resistant to DDAVP treatment? (2)

Answer 13

1. Use a diuretic, because you want to produce natriuresis.

2. Restricting dietary Na+ intake will also help.

Question 14

What is the high urine flow in DI associated with?

Answer 14

Low rates of solute excretion

Question 15

What is the difference between osmotic diuresis and DI?

Answer 15

1. Osmotic diuresis has a HIGH rate of solute excretion that results in polyuria (a lot of urine).
2. DI has a LOW rate of solute excretion that still results in polyuria.

Question 16

What is happening during chronic renal failure?

Answer 16

Decreasing numbers of healthy nephrons are responsible for excreting the same amount of solutes that a healthy kidney normally excretes.

Question 17

What are the 3 causes of osmotic diuresis?

Answer 17

1. Chronic renal failure
2. Diabetes mellitus
3. Administration of poorly re-absorbable solutes (ex. mannitol)

Question 18

What is diabetes mellitus?

Answer 18

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.

Question 19

What is primary polydipsia?

Answer 19

Psychoneurotic disorder where patients drink a crapload of water.

Question 20

What is the treatment for primary polydipsia? What is a downside of this?

Answer 20

Drink less water genius!

Downside: limiting water intake can aggravate a patient with DI