Polydipsia/ Polyuria

Question 1

Does Polydipsia definitively indicate renal disease?

Answer 1

No- can also be influenced by diet, environmental temperature etc.

Question 2

A polydipsic/ polyuric dog is drinking too much because …

Answer 2

it’s unable to concentrate its urine volume normally

Question 3

What general problems can cause Primary Polydipsia? (4)

Answer 3

Neurological- anything affecting behaviour or the thirst centre in the brain
Medications- e.g. Prednisolone
Cushing’s Syndrome
Liver Disease

Question 4

What is a normal urine specific gravity for animals?

Answer 4

anything from 1.001> 1.050

Question 5

In dehydrated or azotemic animals what should the urine specific gravity be greater than?

Answer 5

1.03

Question 6

What do we mean by Isosthenuric?

Answer 6

increased filtration by nephrons leading to high urinary volume that overwhelms the resorptive capacity

Question 7

What are some examples of Extra Renal Factors that cause impaired renal concentrating ability?

Answer 7

• Inadequate numbers of functioning nephrons
• Dysfunction of the collecting tubule (e.g. not enough ADH or abnormal sensitivity to ADH)
• Osmotic Diuresis - osmotically active particles in the filtrate

Question 8

What may cause a reduced number of nephrons that function incorrectly? (2)

Answer 8

Electrolyte abnormalities- hypocalcaemia, hypokalaemia
Endotoxemia e.g. pyometra, upper URT infections

Question 9

What is Vasopressin’s role in renal concentrating ability?

Answer 9

V2 receptor activates cytoplasmic aquaporin 2 which moves to the tubular luminal membrane and allows tubular water resorption