Approach to PU/PD Flashcards

1
Q

Define polyuria

A

> 50ml/kg/day of urine

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2
Q

define polydipsia

A

> 100ml/kg/day intake (dogs)
50ml/kg/day (Cats)

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3
Q

what are the main differentials for primary polydipsia

A

centrally mediated disease (neoplasia, endocrine effects, compensating for losses)
OR
physiology ( toxicity, exercise, high temps)

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4
Q

what does ADH do

A

increases aquaporin density and increases reabsorption from tubules.

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5
Q

what is osmotic diuresis

A

if urine contains solutes above normal values (e.g. glucose in diabetes mellitus) this ‘draws’ water into the tubules increasing output.

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6
Q

what is medullary solute washout

A

loss of solutes from the medulla, also leads to a concentration gradient and osmotic water loss.

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7
Q

how can increased GFR lead to polyuria

A

hypertension will lead to increased filtration in excess of the kidneys resorptive capability.

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8
Q

Is primary nephrogenic diabetes insipidus common

A

No rare

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9
Q

what are the 2 substances that commonly cause osmotic diuresis

A

glucose
sodium

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10
Q

describe Fanconi’s syndrome

A

Proximal tubular disease and loss of glucose, but amino acids, bicarb, electrolytes, lactate, etc.- basically animasl looses ability to reabsorp anything

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11
Q

List 2 things that can cause reduced medullary/interstitial tonicity

A

low protein diet
medullary washot

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12
Q

what is a Phaeochromocytoma

A

Catecholamine producing tumour of the adrenal gland i.e. adrenaline
RARE

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13
Q

If you see signs of dehydration in animal that is PU/PD what is most likely cause

A

primary polyuria

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14
Q

If you see a USG with >1.030 with normal hydration in PU/PD patient what should you think

A

normal- owner wrong
or
primary polydipsia driving intermittent polyuria-

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15
Q

If you see a USG with >1.030 with dehydration what should you think

A

animal is normal and dehydrated
OR
check for:
- glucosuria- diabetes mellitus
- Fanconis
- renal tubular glycosuria

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16
Q

If you see a USG with <1.030 with normal hydration what should you think

A

Consider primary polydipsia again, but consistently present.
means that they are pushing more fluid through kidneys

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17
Q

If you see a USG with <1.030 with dehydration what should you think

A

Consider primary polyuria and intrinsic renal disease or extrinsic disease affecting renal function.

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18
Q

If you see a USG with <1.006 (Hyposthenuria what should you think

A

Diabetes insipidus
primary polydipsia
hypercalcemia
hyperadrenocorticism

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19
Q

what is considered active dilution by kidneys

A

<1.006 USG

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20
Q

what do you do if you suspect primary polydipsia

A

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

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21
Q

describe how to work out osmalility of blood

A

(Na + glucose + BUN) x 2 = osmolality
all values straight from biochem

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22
Q

what is the normal osmalalility of blood

A

dog 290-310
cat 308-335

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23
Q

what is azotaemia

A

elevated urea and creatinine

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24
Q

what is warning sign for a phaeochromocytoma

A

inappropriate hypertension
because it —> Produces adrenaline —> vasoconstricts peripheral vessels —-> increasing central blood pressure

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25
Q

describe what causes pre-renal azotaemia

A

fluid loss i.e. haemoconcentration and reduced renal blood flow (eventually becomes renal also due to renal hypoxia)

give fluids

26
Q

what can cause post-renal azotaemia

A

obstruction or uroabdomen

27
Q

why is post renal azotaemia dangerous

A

Hyperkalaemia can develop rapidly—> bradycardia

28
Q

what can cause renal azotaemia

A

AKI
or
chronic renal failure

29
Q

describe the difference in phosphorus between AKI and CKD

A

AKI- – Phosphorous increase is marked.
CKD- Phosphorous increase is more moderate, and consistent with the creatinine elevation

30
Q

describe how to tell the difference between AKI and CKD

A

phosphorus
clinical signs
CKD- 2/3rd renal mass loss
anaemia- CKD- due to reduced EPO production

31
Q

what does water deprivation test differentiate between

A

primary polydipsia, central diabetes insipidus and nephrogenic diabetes insipidus.

32
Q

what do you see with water deprivation test with primary polydipsia

A

USG improves with just water deprivation

33
Q

what do you see with water deprivation test with central diabetes insipidus

A

USG improves with vasopressin (ADH)

34
Q

what do you see with water deprivation test with nephrogenic diabetes insipidus

A

USG never improves

35
Q

which is more commonly the primary issue, polyuria or polydipsia

A

polyuria

36
Q

what can cause primary polyuria

A

Intrinsic renal issue or extrinsic effect on kidneys

-ADH decrease
osmotic diuresis
medullary solute washout
interstitial tonicity reduction
increased GFR
CKD
AKI

37
Q

what is interstitial tonicity reduction

A

reduced concentration gradient across the interstitium

38
Q

what can cause a decrease in ADH

A

no ADH production - central diabetes insipidus
OR
reduced ADH sensitivity - nephrogenic diabates insipidus

39
Q

what is central diabetes insipidus

A

no ADH production or release

40
Q

what is nephrogenic diabetes insipidus

A

reduced ADH sensitivity or response

41
Q

List some common causes of secondary nephrogenic diabetes insipidus

A

cushings
Addisons
hyperthyroidism
pyometra
hypercalcaemia
drugs

42
Q

what can cause a post obstructive diuresis

A

blocked cats

43
Q

what diagnostic test distinguishes between primary PU or PD

A

USG

44
Q

what does a low osmolality indicate

A

primary polydipsia

45
Q

List some diagnostic tests to look for a PD cause

A

history
POCUS
bloods
neuro exam

46
Q

how can we identify renal azotaemia

A

USG will be isosthenuric, electrolyte disturbances are likely present

47
Q

why is the water deprivation test controversial

A

if you do the test and your animal is polyuric, not polydipsic, it will die

48
Q

how can you differentiate between psychogenic polydipsia and diabetes insipidus

A

modified water deprivation test and ADH administration

49
Q

What are the possible mechanisms behind primary polyuria?

A

ADH or its receptor,
Osmotic diuresis,
Medullary solute washout
Interstitial tonicity reduction
increased GFR

50
Q

List the 5 main differentials for polyuria caused by reduced ADH sensivity/response?

A

Cushings
addisons
hyperthyroidism
pyometra
hypercalcaemia

51
Q

What are the main differentials for polyuria caused by osmotic diuresis?

A

Diabates Mellitus
post-obstructive diuresis- e.g. blocked cats
Addison’s
result of diuretics

52
Q

What disease is common in Basenjis relating to glucose diuresis causing a proximal tubular disease?

A

Fanconi’s syndromes

53
Q

What do we want to look for on clinicial exam with the PU/PD patient?

A

Body condition
signs of dehydration
neuro-signs
dermatological conditions
signs of other body systems

54
Q

Why is it important to do a POCUS with a PU/PD patient with suspected primary PD?

A

Rule out third space loss

55
Q

What next steps would we undertake with a PU/PD patient with suspected primary PU?

A

Triage if needed, POCUS, urinalysis, biochem and haem, bp, further imaging +/- FNA/renal biopsy

56
Q

How do we rule out pre-renal azotaemia

A

give fluids and see if urea and creatinine restore to normal

57
Q

What is the top differentials for pre-renal azotaemia

A

Addisons

58
Q

How do we diagnose an obstruction or uroabdomen?

A

POCUS to check for blockages or free fluid

59
Q

Why can CKD result in non-regenerative anaemia?

A

Due to damage, kidneys produce less EPO (erythropoietin) = less RBC are produced`

60
Q

what do you when performing a water deprivation test

A

over 3-5days you can gradually restrict water and then complete removal of water until 5% dehydration is achieved. If doesn’t improve give ADH (vasopressin).