Approach to PU/PD Flashcards
Define polyuria
> 50ml/kg/day of urine
define polydipsia
> 100ml/kg/day intake (dogs)
50ml/kg/day (Cats)
what are the main differentials for primary polydipsia
centrally mediated disease (neoplasia, endocrine effects, compensating for losses)
OR
physiology ( toxicity, exercise, high temps)
what does ADH do
increases aquaporin density and increases reabsorption from tubules.
what is osmotic diuresis
if urine contains solutes above normal values (e.g. glucose in diabetes mellitus) this ‘draws’ water into the tubules increasing output.
what is medullary solute washout
loss of solutes from the medulla, also leads to a concentration gradient and osmotic water loss.
how can increased GFR lead to polyuria
hypertension will lead to increased filtration in excess of the kidneys resorptive capability.
Is primary nephrogenic diabetes insipidus common
No rare
what are the 2 substances that commonly cause osmotic diuresis
glucose
sodium
describe Fanconi’s syndrome
Proximal tubular disease and loss of glucose, but amino acids, bicarb, electrolytes, lactate, etc.- basically animasl looses ability to reabsorp anything
List 2 things that can cause reduced medullary/interstitial tonicity
low protein diet
medullary washot
what is a Phaeochromocytoma
Catecholamine producing tumour of the adrenal gland i.e. adrenaline
RARE
If you see signs of dehydration in animal that is PU/PD what is most likely cause
primary polyuria
If you see a USG with >1.030 with normal hydration in PU/PD patient what should you think
normal- owner wrong
or
primary polydipsia driving intermittent polyuria-
If you see a USG with >1.030 with dehydration what should you think
animal is normal and dehydrated
OR
check for:
- glucosuria- diabetes mellitus
- Fanconis
- renal tubular glycosuria
If you see a USG with <1.030 with normal hydration what should you think
Consider primary polydipsia again, but consistently present.
means that they are pushing more fluid through kidneys
If you see a USG with <1.030 with dehydration what should you think
Consider primary polyuria and intrinsic renal disease or extrinsic disease affecting renal function.
If you see a USG with <1.006 (Hyposthenuria what should you think
Diabetes insipidus
primary polydipsia
hypercalcemia
hyperadrenocorticism
what is considered active dilution by kidneys
<1.006 USG
what do you do if you suspect primary polydipsia
Could this just be physiological
Toxin exposure
GI losses
rule out 3rd space loss- POCUS
check fro haem and biochem- look for endocrine and osmolarity changes
describe how to work out osmalility of blood
(Na + glucose + BUN) x 2 = osmolality
all values straight from biochem
what is the normal osmalalility of blood
dog 290-310
cat 308-335
what is azotaemia
elevated urea and creatinine
what is warning sign for a phaeochromocytoma
inappropriate hypertension
because it —> Produces adrenaline —> vasoconstricts peripheral vessels —-> increasing central blood pressure