Diabetes insipidus

Question 1

two main types of Diabetes Insipidus

Answer 1

1. Pituitary (central)
2. Nephrogenic

Question 2

ADH/vasopressin₂ receptors

Stimuli for release

Answer 2

• distal segment of kidney

Stimuli

• osmotic stimulus (inc blood osmolality)
• Volume stimulus (hypovolemia, dec CO)

Question 3

Diagnostic criteria

Answer 3

• Hx PU/PD
• Normal PE
• Normal chemistries
• Hyposthenuric < 1.008

Question 4

Rule outs for PU/PD

Answer 4

1. Diabetes Mellitus
2. Cushings
3. Chronic renal dz
4. Pyo
5. Drugs
6. Addison’s

Question 5

Diagnostic tests to differentiate DI and psychogenic Polydypsia

Answer 5

• Water deprivation test => easiest
  
  • avoid hypertonicity, hypervolemia 6-24 hrs
  • don’t let lose more than 3% body weight
• Vasopressin Test
• Combined WD/VT
• ADH trial

Question 6

Differentiate central and nephrogenic DI

Answer 6

• Water deprivation test distinguishes DI from PPD
• Vasopressin test distinguishes Pit from Nephrogenic DI
  
  • if animal responds (concentrates urine) to vasopressin test dx is Pit DI

Question 7

adverse affects of water dep test

Answer 7

• Hypertonic encephalopathy
  
  • if dog loses 3-5 % of body weight can become hypernaetremic and show CNS signs

Question 8

DI TX pit

Answer 8

• DDAVP
  
  • tabs, SQ, eye drops
  • very expensive

Question 9

TX Nephrogenic Diabetes Insipidus

Answer 9

• Chlorothiazide
  
  • diuretic
• Low sodium diet