Liver Function Tests

What are the functions of the liver?

• production of bile

• energy metabolism

• detoxification

• storage of macronutrients

• production of coagulation factors and acute phase protiens

What substances are removed from the body by the liver?

Bilirubin, bile acids, cholesterol, exogenous substances, ammonia

What substances are synthesized by the liver?

• albumin

• urea

• cholesterol

• globulins

• coagulation factors

How is heme broken down into bilirubin?

Heme → fe and protoporphyrin → biliverdin → bilirubin

How does hepatocytes prevent efflux of bilirubin back into the blood?

attaches to ligandin in the cytoplasm

What makes bilirubin water soluble?

conjugation with glucoronic acid

What is it called when bilirubin is secreted in feces?

stercobilinogen

Total bilirubin =

unconjugated + conjugated bilirubin

Unconjugated bilirubin is _____-bound

protien

How can you measure conjugated bilirubin?

• diazo reaction

• urine dipsticks

Why do urine dipstick only measure conjugated bilirubin?

it needs to be water-soluble to be found in urine

When do tissues become visibly yellow from hyperbilirubinemia?

>2.5-3mg/dL

Icterus

yellow discoloration to plasma, bodily fluids, or tissue

Jaundiec

yellow discoloration of tissue

• most visible in pinna, MM, sclera, and inguinal skin

True or False: Jaundice can persist after serum bilirubin returns to normal due to slow degradation.

TRUE

True or False: Dogs/Cats are more naturally icteric than horses/cattle.

FALSE

True or False: Bilirubin is a component of bile.

TRUE

Pre-Hepatic Hyperbilirubinemia causes:

• hemolysis / hemolytic anemia

Hepatic Cause of Hyperbilirubinemia

Cholestasis within the liver

• Hepatitis, Abscesses

• Hepatic lipidosis

• decreased functional liver mass (PSS/cirrhosis)

• neoplasia

• Functional cholestasis

Post hepatic causes of hyperbilirubinemiaa

Cholestasis after liver in the biliary tree

• gallbladder obstruction: choleliths, mucocele, tumors

• Biliary tree obstruction: choleliths, pancreatitis, tumors

In pre-hepatic hyperbilirubinemia, the rate of production of unconjugated bilirubin _______ hepatic uptake.

exceeds

Fasting hyperbilirubinemia is commonly seen in:

horses

In hepatic cholestasis, rate of bilirubin conjugation ______ excretion into bile.

exceeds

In prehepatic hyperbilirubinemia, you would/would not see bilirubinuria.

would not

If you see hyperalbunemia with hemoglobinuria, what type is it?

Pre hepatic caused by intravascular hemolysis

True or False: Intrahepatic cholestasis is more common in dogs and cats than large animals.

TRUE

What elevations will you see with a dog with hepatic hyperbilirubinemia?

• conjugated bilirubin

• ALP/GGT (before bilirubin)

• ALT/AST/SDH from bile acids damaging hepatocytes

What is functional cholestasis?

acute very severe syetmic disease (sepsis) that causes issues transporting bile due to decreased production and secretions

What will you see in a patient with functional cholestasis?

• high Total bilirubin

• minimal inccreae in ALP and GGT

• increased ALT

• inflammatory leukogram

  • leukopenia

  • neutropenia

  • degenerative left shift

Which category of cholestasis can have the highest total bilirubin?

Post-hepatic

Bilirubinuria is common in obstructive cholestasis and in health in what species?

Cattle

True or False: Any increase in bilirubin in cat urine is significant.

TRUE

WHen is it nomal to see trace bilirubin in urine of dogs?

male dogs or dogs with concentrated urine

How much of the liver can be removed before hepatic insufficiency is apparent.

70%

True or False: Animals with acute disease are usually icteric while they are usually not with chronic disease.

FALSE - opposite is true