Cross Species - Chemistry, Liver & Muscle

Question 1

what on a chemistry panel provides information on hepatocellular damage?

Answer 1

hepatocellular enzymes

Question 2

what on a chemistry panel provides information on cholestasis?

Answer 2

bilirubin, cholesterol, & hepatobiliary enzymes

Question 3

what on a chemistry panel provides information on hepatic function?

Answer 3

BUN, albumin, glucose, cholesterol, & bilirubin

Question 4

T/F: hepatic enzymes do not assess hepatic function

Answer 4

TRUE

Question 5

___ is the primary indicator of hepatocellular injury in dogs & cats

Answer 5

ALT

Question 6

in what animals is ALT not useful?

Answer 6

not useful in pigs or large animals

Question 7

where is ALT found in the body?

Answer 7

hepatocyte cytoplasm - increases in serum when cell damage causes leakage, non-specific for type of liver injury

Question 8

what does ALT do in acute hepatocellular injury?

Answer 8

levels will peak at 48 hours & then will decrease after the injury’s stimulus is removed

Question 9

how are increases in ALT quantified?

Answer 9

2-3X is mild, 4-5X is moderate, & greater than 10X is marked

Question 10

___ is an indicator of liver & muscle damage in large & small animals

Answer 10

AST

Question 11

where is AST found in the body?

Answer 11

liver, muscle, erythrocytes, & cardiac muscle

Question 12

what does ALT stand for?

Answer 12

alanine aminotransferase

Question 13

what does AST stand for?

Answer 13

aspartate aminotransferase

Question 14

what are the different half lives for AST between species?

Answer 14

dog: 22 hours, cats: 100 minutes, horses: 7-8 days, & cattle: 1 day

Question 15

how do you determine if an increase in AST is indicative of hepatocellular damage?

Answer 15

look for a concurrent increasein ALT/GGT or SDH in large animals

Question 16

how do you determine if an increase in AST is indicative of a myopathy?

Answer 16

look for concurrent CK increase, AST has a longer half life than CK so it will be increased longer

Question 17

other than liver & muscle injury, what causes an increased AST?

Answer 17

in vitro or in vivo hemolysis

Question 18

what enzyme is the test of choice for hepatocellular injury in horses & cattle?

Answer 18

SDH

Question 19

why is it important to keep in mind the half life of SDH?

Answer 19

short half life of 12 hours, so decreases rapidly when injury’s stimulus is removed - will increase within 24 hours of injury and isn’t specific for injury type

Question 20

what does SDH stand for?

Answer 20

sorbitol dehydrogenase

Question 21

measuring GLDH is done in what animals?

Answer 21

large animals & exotics

Question 22

what does GLDH stand for?

Answer 22

glutamate dehydrogenase

Question 23

where is GLDH found in the body? why is it important to consider the half life?

Answer 23

found in the mitochondria from damaged/necrotic hepatocytes - damage must be severe enough to affect the mitochondria & the short half life is important because it will decrease rapidly when the stimulus is removed

Question 24

what does ALP stand for?

Answer 24

alkaline phosphatase

Question 25

___ is a sensitive indicator of cholestasis in dogs & cats

Answer 25

ALP

Question 26

what are the major isoforms of ALP in dogs?

Answer 26

bone, intestinal, & renal

Question 27

why is ALP less sensitive of an indicator in dogs?

Answer 27

there is a steroid induced enzyme that commonly increases with exogenous or endogenous steroids

Question 28

is serum ALP specific? why?

Answer 28

nope - it measures all isoforms

Question 29

what is the primary source of ALP in animals?

Answer 29

biliary tract epithelium that is induced with cholestatic disease

Question 30

when may you see an increase in the bone isoform of ALP

Answer 30

increases with osteoblast activity, common in young animals but negative prognostic indicator for animals with osteosarcoma

Question 31

what does an increase in GGT indicate?

Answer 31

biliary hyperplasia, structural cholestasis, & biliary necrosis in all vet species

Question 32

what does GGT stand for?

Answer 32

gamma glutamyl transferase

Question 33

where is GGT primarily found in the body?

Answer 33

primarily on biliary epithelial cells, serum measurement is liver specific

Question 34

T/F: an increase in GGT of a dog can be steroid induced

Answer 34

TRUE

Question 35

how is GGT used in calves?

Answer 35

there is a large amount in colostrum, so sensitive indicator of passive transfer

Question 36

___ is a more sensitive indicator of liver disease in cats than ALP

Answer 36

GGT

Question 37

what is the exception for GGT being a more sensitive indicator of liver disease in a cat?

Answer 37

hepatic lipidosis - GGT usually normal but ALP increased

Question 38

how is GGT used in cattle? what toxicity is it a marker of?

Answer 38

assess biliary disease & marker of pyrrolizidine alkaloid toxicity - once activated can remain high or be slow to decrease for months after other values have returned to normal

Question 39

what are the 2 main forms of bilirubin in the blood?

Answer 39

unconjugated & conjugated

Question 40

where is unconjugated bilirubin produced? what is it bound to? where does it undergo conjugation?

Answer 40

predominant insoluble form - made in macrophages from breakdown of heme groups of hemoglobin which is then bound to albumin in plasma & transported to the liver where it undergoes conjugation

Question 41

where is conjugated bilirubin produced? what does it do? where is it normally excreted?

Answer 41

produced in the liver where it becomes soluble, normally excreted in bile so very small amounts in blood, can be excreted in urine because it is water soluble

Question 42

why is bilirubinuria always abnormal? what animal is an exception to this?

Answer 42

dogs can have a small amount of bilirubin in their urine & be normal

Question 43

what is the predominant form of bilirubin in the blood?

Answer 43

unconjugated

Question 44

how is bilirubin excreted?

Answer 44

excreted into the intestines

Question 45

what may causea false increase in bilirubin?

Answer 45

sample hemolysis and/or lipemia

Question 46

when is clinical icterus seen?

Answer 46

when bilirubin is greater than 3 mg/dl

Question 47

what is the prehepatic etiology for hyperbilirubinemia?

Answer 47

increased unconjugated bilirubin due to increased breakdown of hemoglobin most commonly seen with IMHA - may see concurrent increase in conjugated bilirubin if there is concurrent cholestasis

Question 48

what is the hepatic etiology for hyperbilirubinemia?

Answer 48

abnormal hepatic uptake or conjugation of bilirubin - typically increased unconjugated

Question 49

what is the posthepatic etiology for hyperbilirubinemia?

Answer 49

disruption of bile flow due to gallbladder disease, bile duct, or duodenal biliary papilla (extrahepatic biliray obstruction) with bilirubin seen in the urine before being seen in the serum

Question 50

T/F: you can't always delineate the type of hyperbilirubinemia based on unconjugated & conjugated bilirubin because the pathways overlap

Answer 50

TRUE

Question 51

how are horses different with their unconjugated bilirubin?

Answer 51

unconjugated bilirubin increases with decreased feed intake starting at 12 hours, can increase to 10-12 mg/dl within 2-4 days of fasting

Question 52

how does the liver produce bile acids? where is it stored? what animals are the exception for storage?

Answer 52

liver produces bile acids from cholesterol & then stores it in the gallbladder where it undergoes enterohepatic circulation - horses are the exception because they don't have a gallbladder

Question 53

how do bile acids undergo enterohepatic circulation?

Answer 53

excreted into the intestines & then reabsorbed by portal vascular system & taken up by hepatocytes for re-excretion into the intestines

Question 54

T/F: dogs & cats are the only animals that have low blood levels of bile acids that are normal when fasted

Answer 54

TRUE

Question 55

postprandial gallbladder contraction has what affect on bile acids?

Answer 55

increases bile acid excretion into the intestines so blood concentration increases

Question 56

what is the purpose of measuring bile acids?

Answer 56

to assess portal blood flow & hepatic function

Question 57

why not measure bile acids in a small animal with increased bilirubin unless suspeted to be prehepatic?

Answer 57

doesn't provide any additional information because bilirubin & bile acids are excreted by the same pathway

Question 58

what is the purpose of running a bile acids panel on a young animal?

Answer 58

support diagnosis of a liver shunt - usually see high postprandial levels

Question 59

T/F: intestinal disease can cause a mild to moderate increase in bile acids of small animals

Answer 59

TRUE

Question 60

why should you always evaluate the highest level of bile acids in small animals regardless of timing?

Answer 60

in some patients, preprandial concentration is higher than postprandial due to spontaneous gallblader contraction

Question 61

what is the test protocol for bile acids of small animals?

Answer 61

fast them for 12 hours, draw your pre sample, feed the, wait two hours, draw post sample

Question 62

T/F: because horses lack a gallbladder, a single level measurement of bile acids is sufficient

Answer 62

TRUE

Question 63

how is ammonia made in the body? how is it excreted?

Answer 63

gi microorganisms predominantly in the large intestines convert dietary amino acids and urea into ammonia where it is absorbed into portal circulation, taken up by hepatocytes, & converted to urea via the urea cycle & excreted

Question 64

why do you need to measure ammonia levels immediately on an in-hospital analyzer?

Answer 64

very unstable

Question 65

increased ammonia levels in a dog is supportive of what?

Answer 65

supports diagnosis of hepatic encephalopathy with suspected liver disease & neuro signs (shunt)

Question 66

why may you have increased ammonia levels from a ruminant?

Answer 66

due to overgrowth of urea-producing bacteria in the rumen or consumption of excessive non-protein nitrogenous compounds (urea toxicosis)

Question 67

what are the 2 main etiologies of hyperammonemia in horses?

Answer 67

hepatic encephalopathy with suspected liver disease & neuro signs & diarrhea causing bacterial overgrowth in large intestines without liver disease

Question 68

what is creatine kinase? what is it used for?

Answer 68

leakage enzyme present in myocyte cytoplasm in high concentration - marker of skeletal or cardiac muscle injury (hemolysis also increases concentration)

Question 69

T/F: a cat may have mild to moderate increases in CK when they are sick

Answer 69

TRUE

Question 70

what is an example of a cause of very high CK levels in a cow?

Answer 70

downer cow

Question 71

what are some causes of increased CK in horses? how do you assess this?

Answer 71

exertional myopathies & post-surgical increases due to recumbency - evaluate in conjunction with AST