Lab Evaluation of the Liver Flashcards
What are the 3 things we can detect with lab eval of liver dz?
hepatocellular injury
cholestasis
liver failure
At what % of liver function loss would you see failure to eliminate and synthesize substances?
70-80%
When detecting hepatocellular injury what enzymes do you look at?
leakage enzymes alt ast sdh gldh
Is ALT liver specific?
Yes! Except for in cases of severe muscle damage.
If you have a high ALT and you send the liver out for biopsy and the biopsy comes back normal, what’s going on?
Either the animal is transiently hypoxic (happens alot with anemic animals) or
Mild membrane changes that you can’t see with the microscope
Increased in AL in middle aged-old dogs indicates _____.
Young dogs ______
old/middle aged: chronic hepatitis
young: portocaval shunt
Is AST liver specific
nope, it also comes from muscle
usually returns to normal faster than alt in dogs
How do you eval liver in large animals?
SDH (though it has a short half life) or
GLDH (expensive!)
ALT and AST are not liver specific in horses
What would you see in focal vs diffuse hepatic necrosis?
focal- nothing
diffuse: increase in leakage enzymes, induced enzymes, and bile acids
if >60-80% affected, liver function tests abnormal
What are the markers of cholestasis and drug induction
ALP and GGT
Increases in ALP in dogs indicate (3 things)
Young, large breed dogs: bone growth
liver: choleostasis
corticosteriod induced
Increased ALP in cats indicate
choleostasis
hyperthyroidism
Can topical corticosteriod ear ointments cause an increase in ALP
yep!
You have an increased ALP without hyperbilirubinemia, what do you suspect?
ALP increase from steriod (endogenous or exogenous) or anticonvulsant medication
GGT is induced by
cholestasis (cats!, except hepatic lipidosis), steriods, hepatic injury
Markers of choleostasis
leakage enzymes mildly inc induced enzymes marked inc serum bilirubin marked/mod inc bile acids inc other liver function tests normal
4 dz’s associated with cholestasis
cholangitis
cholangiohepatitis
bile duct obstruction
hepatic lipidosis
What are the 3 things that can cause bilirubin to increase?
increased production due to rbc destruction (prehepatic)
decreased uptake or conjugation (hepatic)
blockage of bile flow (choleostasis)
What are 3 things that cause bile acids to increase?
deviation of portal circulation
decrease in hepatocyte uptake
decreased bile excretion in bile with subsequent regurgitation into blood
What would cause an increase in cholesterol?
cholesterol is a precursor to bile acids so if the liver is not working correctly then cholesterol can increase, especially with choleostasis
Why does ammonia increase in dogs with liver failure and what clinical signs would you see?
Normally ammonia is drained from the gut via the portal vein and converted to urea. If there’s liver damage, it wont get converted and it goes into circulation causing CNS signs (dementia and head pressing).
How much of liver function is lost if the patient is hypoalbumenic?
60-80%
Would globulin decrease in liver failure?
Not really, it’s made by mostly lymphoid tissue
What would you see with BUN in liver failure?
decrease because less ammonia is being converted to urea
What would you see with cholesterol in liver failure?
decrease because the liver is the main site of synthesis
What would you see with cholesterol in choleostasis?
increase, bile is the major route of cholesterol excretion
What happens to coag factors in liver failure?
At the end of liver failure they are decreased in production-> often the thing patients die from is bleeding to death
How would choleostasis causes a patient to bleed to death?
bile flow is nessecary for absorption of vit k factors (1972!) so if there’s complete choleostasis patient can bleed because there’s no vitamin k
What would you see with an early portosystemic shunt?
enzymes may/may not be increased
mildly increased ALP
bile acids increased
microcytic anemia (sometimes)
What would you see with a late portosystemic shunt?
liver failure -> decreased alb, BUN, glu, cholesterol, coag factors
inc bile acids
maybe choleostasis: incr bilirubin, ALP
microcytic anemia
Liver functions tests are normal until ________ function lost
60-80% lost
