Concepts of Liver Disease

Question 1

what are the functions of the liver?

Answer 1

• metabolic filter
• remove translocated intestinal bacteria
• carbohydrate, lipid, vitamin, protein metabolism
• immunologic function
• detoxification and excretion
• makes and releases bile acids

Question 2

describe the functional anatomy of the liver

Answer 2

• bile ducts flow parallel yet in opposite direction of the artery and vein
• hepatic lobule has a hepatic vein in the center, surround by sinusoids, portal triads on the edges
• triad made of bile duct, hepatic arteriole, portal venule
• sinusoids framed by hepatocytes, web-like structure between central vein and portal triad
• Kupffer cells in sinusoid lumen (specialized macrophages)
• Stellate cells in perisinusoidal space, involved in liver fibrosis, unclear role

Question 3

what are the signs of liver disease?

Answer 3

very variable, inappetance, lethargy, vomiting, jaundice (most specific), change in liver size/contour/margins

Question 4

ascites and liver disease

Answer 4

• low protein ascites (<2.5 g/dL)
  
  • portal hypertension
  • hypoalbuminemia
• high protein ascites (>2.5 g/dL)
  
  • right-sided heart failure
  • caval syndrome

Question 5

which liver enzymes indicate cell damage?

Answer 5

ALT, AST

increase with necrosis, poor correlation between magnitude of increase and severity of disease

Question 6

which liver enzymes are induced by cholestasis or drugs?

Answer 6

ALP (half life of 6 hours in cats so if its there, be worried)

GGT

Question 7

what are the signs of high bilirubin

Answer 7

icterus/jaundice

Question 8

what are the three categories of hyperbilirubinemia?

Answer 8

pre-hepatic

hepatic

post-hepatic

Question 9

what is the difference between dogs and cats with regard to bilirubinuria?

Answer 9

normal in low levels in dogs urine (low kidney threshold)

cats have high threshold so if bilirubin seen in urine, be worried

Question 10

how do albumin levels change with liver disease?

Answer 10

decrease since albumin is made by liver, should not go down with anorexia/fasting

Question 11

how does BUN change with liver disease?

Answer 11

decrease but could also be due to decreased appetite, low protein diet, diuresis

Question 12

how do glucose levels change with liver disease?

Answer 12

decrease because liver is responsible for gluconeogenesis

Question 13

how do cholesterol levels change with liver disease?

Answer 13

decreased because liver normally uptakes and synthesizes, increased with cholestatic disease!

Question 14

how do blood ammonia levels change with liver disease?

Answer 14

increase because normal liver should convert ammonia to urea, can increase with fasting

if normal when fasting, may still have liver disease!

Question 15

how do serum bile acids change with liver disease?

Answer 15

not needed if patient is icteric

doesn’t contribute to encephalopathy

liver function test not but does not differentiate between type of liver disease

very high post-prandial with shunts

Question 16

what additional tests are used to diagnosed liver disease?

Answer 16

• complete blood count
• clotting function
• fecal to check for GI bleeding
• radiographs to evaluate liver size (microhepatica, ascites)
• abdominocentesis (check for bile)
• ultrasound (only good for focal lesion or obstruction)
• aspiration of liver (cancer, hepatic lipidosis check)
• liver biopsy (good for more specific diagnosis)

Question 17

what percentage of liver can be removed before evidence of dysfunction is seen?

Answer 17

75%

Question 18

a dog has an ALT of 780 (ref 10-100) and an ALKP of 220 (10-100).

is this more consistent with hepatocellular or cholestatic disease?

Answer 18

hepatocellular because of magnitude of increase of ALT