CCM 76: Diabetes Insipidus

Question 1

Define PU

Answer 1

UOP > 50 mL/kg/day

Question 2

What type of hormone is AVP and where is it produced and secreted?

Answer 2

• Peptide hormone (i.e., AA < 100)
• Hypothalamus –> axons reach into the posterior pituitary where it is released

Question 3

Where are the hypothalamic osmoreceptors located?

Answer 3

nucleus opticus

Question 4

List causes of acquired central diabetes insipidus

Answer 4

• trauma
• infectious inflammatory (encephalitis)
• neoplasia
• vascular
• immune-mediated
• idiopathic

Question 5

List causes of acquired nephrogenic diabetes insipidus

Answer 5

• Drugs (e.g., vasopressin, aminoglycosides)
• electrolyte abnormalities (hypercalcemia, hypokalemia)
• bacterial infections (E coli, Streptococcus, Leptospirosis)
• degenerative changes (CKD, amyloidosis)
• paraneoplastic (intestinal leiomyosarcoma)

Question 6

Name a class of drugs that can be used to treat nephrogenic diabetes insipidus until the underlying cause can be fully managed

Answer 6

thiazide diuretics - paradoxically decrease total daily urine output only in patients with DI

Question 7

List the equation to calculate to urinary clearance of free water. What is this equation useful for?

Answer 7

Urinary clearance of free water = urine volume x ( 1 - [(Na urine + K urine) / Na plasma ] )

Question 8

What is the main contraindication for DDAVP administration in diabetes insipidus?

Answer 8

severe hypernatremia that would be corrected too fast with DDAVP

Question 9

How much and how fast should urine osmolality increase after giving DDAVP to patients with central DI

Answer 9

within 2-4 hours by 50%

in partial central DI or nephrogenic DI –> 10-50%

if no increase in osmolality likely nephrogenic DI