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BVM3 Alimentary > Lab Diagnostics of Liver Disease > Flashcards

Lab Diagnostics of Liver Disease Flashcards

1
Q

What are the enzymes which indicate hepatocellular damage? Where do these enzymes come from?

A

ALT, AST, SDH, GLDH
Leaked directly from hepatocytes and indicate damage/necrosis of liver cells

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2
Q

What is the hepatocellular enzyme most commonly used for dogs and cats?

A

ALT

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3
Q

How many hours after injury does ALT increase and how long after injury does it peak? Over how long does it decrease?

A

ALT will increase within 12 hours of injury and peaks at 1-2 days post injury and gradually decreases over next 2-3 weeks

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4
Q

What does ALT indicate?

A

ALT = liver damage
T = TRAUMA
Almost completely specific to the liver

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5
Q

Is ALT appropriate to use for large animals?
What values should you use for large animals?

A

No - ALT activity in large animals is very low
Use SDH or GLDH instead

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6
Q

Is AST a liver specific enzyme? Where else can this liver enzyme be derived from? What other enzyme is similar?

A

No - but AST and ALT can be derived from muscle damage and erythrocyte damage (hemolysis)

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7
Q

What do high AST levels indicate?

A

The need for further investigation/testing

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8
Q

What does creatinine kinase (CK) indicate?

A

Muscle-specific enzyme and most sensitive indicator of muscle injury

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9
Q

How long after muscle injury does CK increase? When does it peak and how quickly does it decrease?

A

Will increase within 1-2 hours of injury, peaks at 6-12 hours post, and decreases quickly over next 24-48 hours

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10
Q

What does persistently elevated CK indicate?

A

Ongoing damage

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11
Q

Does ALT/AST change slower or faster than CK?

A

ALT/AST increase and decrease more slowly than CK

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12
Q

If CK is elevated what other issue should you think about besides just muscle damage?

A

Think about concurrent liver damage

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13
Q

What is cholestasis?

A

Obstruction of bile flow with regurgitation of biliary substances into the blood

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14
Q

What are the 2 enzymes which indicate cholestasis?

A

ALP - Alkaline phosphatase
GGT - gammaglutamyltransferase

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15
Q

Where does ALP derive from? When does it increase?

A

Bile duct epithelium
Increases with cholestasis

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16
Q

Why is ALP increased in young animals?

A

ALP found in bone so increased in young growing animals

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17
Q

Where does ALT derive from?

A

Hepatocytes (primarily)

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18
Q

In what species is the steroid induced isoform of ALP found? Why is this significant in sick animals?

A

Steroid induced isoform in dogs only - sick dogs with steroids on board (whether its stress, meds, etc) will have an increase in ALP
Not found in cats - any increase is significant!

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19
Q

What is special about the half-life of ALP in cats?

A

VERY short half-life
VERY difficult to make a significant increase in ALP in cats as it is excreted/degraded quickly

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20
Q

Which 2 conditions in cats could cause an increase in ALP?

A

Hyperthyroidism
Hepatic lipidosis

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21
Q

Where is GGT derived from?

A

Bile duct epithelium

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22
Q

What does GGT indicate in large animals?

A

More sensitive indicator of cholestasis than ALP

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23
Q

Why is GGT increased in nursing animals?

A

Contained in colostrum so will be increased in nursing animals

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24
Q

What level will be increased in the situation of renal tubular damage? Why?

A

GGT present in renal tubular cells so could be found in urine (not blood) if renal tubular damage is present

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25
Q

What does the “T” in ALT mean and the “P” in ALP? What do these values indicate? Which of these values are expressed more easily?

A

ALT - Trauma (comes out of cells very easily)
ALP - Production (needs induction)

26
Q

What are the 7 BW measures of hepatic function?

A
27
Q

What is bilirubin the breakdown product of? Where is it conjugated and excreted?

A

Breakdown product of hemoglobin
Conjugated in the liver and excreted with bile into the gut

28
Q

What is bilirubin converted into before its excreted in the feces?

A

Urobilinogen

29
Q

What substance gives serum/plasma yellow color?

A

Bilirubin

30
Q

What value will increase in horses fasted for 24+ hours?

A

Bilirubin

31
Q

T/F - low levels of bilirubin can be found in normal dog urine

A

True

32
Q

T/F - low levels of bilirubin can be found in normal cat urine

A

False - not normal and is always a significant finding in the cat

33
Q

In cats is an elevation in bilirubin first noticeable in the urine or the blood?

A

Bilirubinuria first noticeable before elevation detected in circulation

34
Q

What are 2 products of protein metabolism detectable on BW?

A

Ammonia and Urea

35
Q

Where is ammonia derived from? How does it travel to the liver? How is it converted to urea?

A

Product of PROTEIN metabolism (from diet)
Ammonia derived from gut and travels to liver via portal circulation
Ammonia is converted to urea via the urea cycle

36
Q

What happens to ammonia in liver failure? What does this mean for the levels of urea?

A

Ammonia is not able to be converted to urea in liver failure –> buildup of ammonium in blood
Urea levels will be decreased, Ammonium will be increased

37
Q

What is the main route of excretion for urea? What system is urea primarily used to evaluate?

A

Primary route of excretion is via the kidneys, hence urea is primarily used to evaluate the renal system

38
Q

In what organ does some production of glucose occur?

A

Liver

39
Q

In what stage of liver disease do decreases in glucose occur? What are some other causes of hypoglycemia?

A

End-stage liver disease
Other causes of hypoglycemia - neoplasia, bacterial sepsis

40
Q

What can cause hyperglycemia?

A

Stress (mild increase)
Diabetes mellitus

41
Q

Is glucose a sensitive indicator of hepatic dysfunction?

A

No

42
Q

Where is cholesterol synthesized? Where is it excreted?

A

Synthesized in the liver and excreted in bile

43
Q

How does cholesterol change in the following situations:
- Hepatic disease
- Cholestasis
- Hepatic failure

A

Hepatic disease - may increase or decrease
Hepatic failure - decrease (due to decreased synthesis)
Cholestasis - increase (due to decreased excretion)

44
Q

What would happen to cholesterol levels if there is biliary obstruction but also liver failure?

A

Cholesterol level will seem unchanged, though there are 2 issues going on

45
Q

How does cholesterol level change post-prandially?

A

Increase

46
Q

How does cholesterol level change with endocrine disorders?

A

Increase in cholesterol with diabetes mellitus and hyperadrenocorticism

47
Q

How does cholesterol change with hyper/hypothyroidism?

A

Varies inversely with T4
- Hypothyroidism = increased cholesterol
- Hyperthyroidism = decreased cholesterol

48
Q

What is the difference between bile and bile acids?

A

Bile flowing from the liver is concentrated in the gallbladder and, in response to a meal, released into the upper intestine.
In the intestines, bile acids act as detergents and help to emulsify fats, aiding in their digestion and absorption.

49
Q

How are bile acids measured?

A

Fasted and post prandial levels measured

50
Q

Where are bile acids stored during fasting? How are they released?

A

Bile acids stored in gallbladder
Released by gallbladder contraction after feeding

51
Q

What does bile acid concentration test?

A

Tests hepatic uptake

52
Q

How is bile acid concentration [BA] tested in horses? What about their anatomy is different from dogs/cats?

A

Horses measure single sample
No gallbladder in horses (no storage)

53
Q

Why is bile acid concentration [BA] not an appropriate test in ruminants?

A

Range is too wide

54
Q

What are the 2 main pathological processes responsible for increase in [BA] in serum or plasma?

A
55
Q

How does bile acid challenge test work?

A

A bile acids “challenge” test with both a pre- and two-hour post-prandial blood collection is recommended over a single fasting or random sample (in dogs and cats) because it has substantially higher sensitivity for detecting disease. Feeding stimulates gall bladder contraction and the release of bile acids into the intestine and eventual portal circulation. This increased load can better “challenge” the liver’s ability to clear the increased bile acids presented to it.

56
Q

What can cause false increases in NH4+ in blood samples?

A

Hemolysis (poor sampling technique)
Delayed sample analysis
Serum (not plasma)

57
Q

What can cause false decrease in NH4+ in blood samples?

A

Exposure to air

58
Q

What are the factors which can cause hyperammonemia?

A
59
Q

T/F - Enzymes and function tests ARE specific enough to determine underlying cause of liver lesion

A

False

60
Q

What do you need to do in order to confirm underlying cause of liver lesion if suspected based on hematology?

A

FNA or Biopsy

BVM3 Alimentary (24 decks)

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