clinical path - liver

Question 1

functions of the liver

Answer 1

metabolism of body fuels 
storage functions 
detoxification 
synthesis of most coagulation proteins 
excretory function

Question 2

what does the liver metabolize

Answer 2

• protein metabolism: albumin, globulin (not immunoglobulin)
• carbohydrate metabolism: remove glucose from portal blood
• lipid metabolism: make fatty acids, triglycerides, cholesterol, and apolipoproteins

Question 3

when does serum enzyme activity increase

Answer 3

when the rate an enzyme enters plasma exceeds the rate of enzyme inactivation or removal from plasma

Question 4

when do you see an increase in enzymes

Answer 4

when there are damaged cells,
induction of enzyme synthesis
cell proliferation (neoplasia)
decreased enzyme clearance (decreased renal blood flow)
or ingestion and absorption (GGT from cholesterol, ALP from bones)

Question 5

what enzymes are released from damaged hepatocytes

Answer 5

ALT
AST
SDH
GLDH

Question 6

What enzymes are associated with cholestasis

Answer 6

ALP

GGT

Question 7

what are the four liver products

Answer 7

urea, glucose, albumin, cholesterol

Question 8

what are some hepatobiliary causes of increased liver enzymes

Answer 8

hypoxia, metabolic disease, toxicoses, inflammation, neoplasia, trauma, or intrahepatic/extrahepatic bile duct obstruction

Question 9

what are some extrahepatic causes of increased liver enzymes

Answer 9

endocrine disease, Gi disorders, systemic infections, or drug indication

Question 10

ALT

Answer 10

sensitive indicator of hepatocellular injury, but not specific (found in small amounts of muscle too)

Question 11

what species can you use ALT

Answer 11

Useful in cats and dogs

not useful in ruminants and horses

Question 12

AST

Answer 12

an unspecific enzyme produced by the liver, muscle, and erythrocytes during hemolysis

Question 13

SDH

Answer 13

primary liver enzyme for horses. can also use in ruminants. unstable in vitro, need to run sample immediately

Question 14

GLDH

Answer 14

liver-specific enzymes helpful in detecting hepatocellular injury/necrosis of large animals/ dogs

Question 15

explain cholestasis

Answer 15

interruption or obstruction of the bile flow or excretion. can be intrahepatic (bile caniliculi and bile ducts) or extrahepatic (gall bladder and common bile duct)
may result in release of ALP and GGT

Question 16

what are the three types of ALP

Answer 16

• B-ALP: bone ALP
• L-ALP: liver ALP
• C- ALP: corticosteroid induced ALP (only in dogs)

Question 17

what can increase B-ALP

Answer 17

• bone growth (young healthy dogs)
• bone fractures (10 days after fracture starts to heal)
• bone lesions that increase osteoblastic activity (osteosarcoma)
• hyperthyroid in cats

Question 18

L-ALP

Answer 18

sensitive indicator of cholestasis in dogs
increased intrabiliary pressure cause increase ALP production by hepatocytes
often seen in conjunction with GGT and bilirubin

Question 19

what enzyme do you use to detect cholestasis in horses and cattle

Answer 19

GGT

Question 20

why is GGT liver sensitive

Answer 20

it is predominately associated with the brush border or microvilli of hepatocytes, biliary epithelial cells, renal tubular epithelial cells or mammary cells

Question 21

GGT detection in different species

Answer 21

• horses: GGT is more sensitive for detecting cholestasis than ALP
• cattle: GGT is more sensitive than ALP for detecting cholestasis
  dogs: ALP is more sensitive than GGT
  cats: GGT may be normal with hepatic lipidosis, but ALP increased

Question 22

explain hepatic insufficiency

Answer 22

pathophysiologic state in which the number of functioning hepatocytes is markedly reduced

Question 23

what are the two disorders causing hepatic failure

Answer 23

1. disorders that destroy hepatocytes

2. PSS causing hyperplasia or atrophy of liver due to decreased nutrients

Question 24

what are the three liver function tests

Answer 24

• bile acids
• ammonia
• bilirubin

Question 25

explain the general physiology of bile acids

Answer 25

bile is synthesized in the liver from cholesterol, conjugated, and secreted into the gall bladder. After a meal, the gall bladder contracts, releasing bile into the intestines. it solubilizes lipids and aids in fat digestion in the intestine when bile acids reach the ileum, it is transported back into the portal circulation and extracted by hepatocytes

Question 26

where are bile acids found?

Answer 26

95% in enterohepatic circulation 5% in the systemic circulation --> increase in systemic concentration indicates a problem somewhere in enterohepatic circulation

Question 27

causes for increased serum bile acids

Answer 27

1) decreased clearance from portal blood - -> decreased heaptic uptake - -> PSS 2) decreased bile acid excretion - -> obstructive choleostasis - -> functional choleostasis

Question 28

bile acid concentrations suggesting liver dysfunction

Answer 28

cats: >20um/l dogs: >25um/l horses: >18um/l cattle: ineffective test

Question 29

ammonia physiology

Answer 29

produced in the GIT by the breakdown of AA and urea by GI microflora, where it's then transported by the portal circulation to the liver and converted into urea. urea is then excreted into the GIT and into the urine

Question 30

where is ammonia found

Answer 30

80-90% is shunted into the urea cycle | 10-20% metabolized by peripheral tissues (kidneys, brain, heart)

Question 31

explain the physiology of bilirubin

Answer 31

bilirubin is a pigment that is produced by the degradation of the heme portion of hemoglobin, mainly by macrophages. it is then transported to the liver where it is conjugated before being excreted into the bile

Question 32

two types of bilirubin

Answer 32

1) unconjugated: not water-soluble, transported in the blood bound to albumin 2) conjugated: water soluble, conjugated to glucuronide

Question 33

what are the three types of hyperbilirubinemia

Answer 33

1) pre hepatic 2) hepatic 3) post hepatic

Question 34

explain pre hepatic hyperbilirubinemia

Answer 34

due to RBC breakdown (haemolysis), resulting in an increase in unconjugated bilirubin that exceeds the hepatic uptake capacity this can cause secondary cholestasis as the liver becomes overwhelmed

Question 35

explain hepatic hyperbilirubinemia

Answer 35

caused by a decreased hepatic uptake or conjugation within the liver can be of a hypoxic, anomalous, metabolic, neoplastic, inflammatory, or inheritated nature

Question 36

explain post hepatic hyperbilirubinemia

Answer 36

extrahepatic disruption of bile causing a partial or complete blockage can be due to neoplasia, cholelithiasis, cholangitis, or inflammation of an adjacent organ, i.e pancreas