Clinical pathology Flashcards
(22 cards)
What is measured to assess liver damage?
Hepatocellular and induced biliary enzymes
What is measured to assess liver function?
Bilirubin and bile acids
What are the 4 hepatocellular enzymes measured to assess liver damage?
Alanine aminotransferase (ALT) Aspartate aminotransferase (AST) Sorbitol dehydrogenase (SDH) Glutamate dehydrogenase (GLDH)
Describe the properties of ALT
- Found in cytosol - Liver specific - Increased ALT due to degenerative change of hepatocytes - Only used in small animals - Increase in circulation, proportional to hepatic mass effected - Poor correlation between serum levels and hepatic dysfunction
Describe the properties of AST
- Isoenzyme - Found in cytosol, mitochondria, RBC, skeletal and cardiac muscle
What else could elevated levels of AST suggest?
Haemolysis or muscle injury
Describe the properties of SDH
- Found in cytosol - Useful in horses and cattle - Degrades v quickly once blood sample is taken *not many labs offer this*
Describe the properties of GLDH
- Found in cytosol - Sensitive marker for hepatic injury - Useful in horses and cattle
What are the 2 biliary enzymes that can be measured to assess liver damage?
Alkaline phosphatase (ALP) Gamma glutamyl transferase (GGT)
Describe the properties of ALP
- Found in hepatocytes in biliary epithelium
- Cholestasis markedly increases ALP activity
- Damage to liver parenchyma induces ALP, increases serum levels
- Increased levels can indicate cholestasis, drug induction (dogs), bone remodelling
Draw a diagram to demonstrate the production of ALP
ALP and cats…
- Produce lot less ALP
- Has much shorter half life
- Steroids don’t induce it
- Elevation is significant
- Indicator of feline hyperthyroidism
Describe the properties of GGT
- Membrane bound enzyme found in hepatobiliary system and renal tubules
- Useful in cttle, horses, cats
- Elevated levels may indicate cholestasis
- In renal disease found in urine
How can hyperbilirubinaemia be classified?
Pre-hepatic, hepatic, post-hepatic
What are the features of pre-hepatic hyperbilirubinaemia?
- Haemolysis occurs causing Hb to degrade to bilirubin
- Circulating [bilirubin] increases
- Liver overwhelmed
- Conjugation with albumin occurs in liver as normal but not at a fast enough rate
What are the features of hepatic hyperbilirubinaemia?
Bilirubin levels increase due to a decreased liver functional mass, i.e. reduction in healthy hepatocytes
What are the causes of post-hepatic hyperbilirubinaemia?
- Obstructive cholestasis (intra/extra hepatic obstruction of bile flow; ability to uptake bilirubin inhibited)
- Functional cholestasis (infection in ducts, affects peristalsis)
Draw a diagram to explain normal bile acid metabolism
Using a diagram explain what happens to bile metabolism with a portosystemic shunt
Using a diagram explain what happens to bile metabolism when there is a reduced hepatic functional mass
Using a diagram explain what happens to bile metabolism during cholestasis
How would you test bile acid levels?
Cats and dogs:
- Fast animal, take a sample then take another 2 hrs post-prandial
- Normal, level should be low in both samples
- Abnormal, increased levels in 2nd sample
Horses:
- Single measurement used as have no gall bladder
