Concepts of Liver Disease

Question 1

Describe the functional anatomy of the liver

Answer 1

• Lobular structure - central veins in the middle, portal triad on the outside
• blood flows from all digestive organs to the liver, then through the portal vein and hepatic a. to central vein, while bile flows the opposite way
• hepatocytes have a ton of organelles - goes along with their high metabolic capability

Question 2

What is the function of the liver?

Answer 2

• Carb, lipid, protein and vitamin metabolism
• immunologic function
• detoxification and excretion (bilirubin, steriods, ammonia, drugs)
• synthesis, regulation and enterohepatic circulation of bile acids

Question 3

What are the signs of liver disease?

Answer 3

• Breed predisposition: Dobies, Spaniels, Labs, Bedlingtons
• evidence of jaundice (most specific)
• low protein ascites (<2.5 g/dL)
  
  • portal hypertension, hypoalbuminemia
• high protein ascites (>2.5 g/dL)
  
  • R-sided heart failure, caval syndrome
• cats: ascites uncommon, palpate thyroid gland and measure T4, copper colored iris in feline shunts, can actually palpate liver abnormalities

Question 4

How much of the liver can be removed before evidence of dysfunction?

Answer 4

75%

Question 5

Describe liver leakage enzymes

Answer 5

• ALT - liver leakage enzyme, almost always > AST
  
  • cytoplasm
  • liver specific
• AST - liver leakage enzyme, takes larger amount of damage to hepatocytes
  
  • cytoplasm and mitochondria
  • other tissues (mm, RBCs)
• Greatest increases seen w/ necrosis
• Poor correlation b/t magnitude of incr and severity of dz

Question 6

What are the liver enzymes that indicate cholestasis or drugs?

Answer 6

• ALP isoenzymes:
  
  • bone, liver, steroid inducible (not in cats)
  • ALP half life in cats only 6 hrs
• GGT: predominately in liver
• Both membrane bound
• Induced by cholestasis, drugs

Question 7

What are the pseudofunction tests?

Answer 7

• bilirubin
• albumin
• BUN
• cholesterol
• Glucose

Question 8

What would cause bilirubin increase and what clinical signs would you see with this?

Answer 8

• C/S: icterus or jaundice, bilirubinuria (conjugated bilirubin, can be normal in dogs, ANY in cats is significant!)
• Causes:
  
  • pre-hepatic
    
    • hemolysis
  • hepatic
    
    • hepatitis, hepatic lipidosis, neoplasia, cirrhosis, toixins/drugs, sepsis
  • post-hepatic
    
    • Pancreatitis, cholangitis, cholecystitis, choleliths, biliary neoplasia, GB mucocele, duodenal dz

Question 9

Describe what would cause a decrease in albumin

Answer 9

• produced by liver
• decr in liver dz
  
  • exclude PLN or PLE
  • bile acids
• little decr in anorexia/fasting

Question 10

Why might you see hypoglycemia with liver disease?

Answer 10

because gluconeogesis and glycogen storage occurs in the liver

Question 11

How might cholesterol concentrations change with hepatic dysfunction vs. cholestasis?

Answer 11

• Uptake and synthesis in liver
• decr in dysfunction
• incr in cholestasic dz

Question 12

What are your true liver function tests?

Answer 12

Ammonia and bile acids

Question 13

What does a low BUN indicate, and what are other potential causes of this?

Answer 13

• Assoc. with ammonia and metabolism
• Low BUN suggests liver dysfunction
  
  • diuresis
  • low protein diet
  • decr appetite

Question 14

What are additional lab studies you can do for liver disease/

Answer 14

• CBC (RBC morphology)
• Clotting function
  
  • BMBT
  • ACT/PTT
  • Prothrombin time
  • Platelet count/function
• Fecal exam
  
  • GI bleeding
• Rads
• Abdominocentesis
• Ultrasound
• Aspiration cytology (important for ascites)
• Biopsy