Clinical Pathology Of The Liver

Question 1

Functions of the liver

Answer 1

• Carbohydrate dynamics
• Lipid metabolism
• Protein metabolism
• Management of endogenous waste from metabolism
• Iron transfer
• Bile production and storage
• Synthesis of coagulation factors
• Metabolism of xenobiotics- drugs

Question 2

Name the hepatocellular (liver) enzymes

Answer 2

• Alanine aminotransferase (ALT)
• Aspartate aminotransferase (AST)
• Sorbitol dehydrogenase (SDH)
• Glutamate dehydrogenase (GLDH)

Question 3

Which 2 types of tube sampling are used for testing the liver

Answer 3

Serum or lithium heparin sample

Question 4

Parameters used investigate liver damage

Answer 4

• Hepatocellular enzymes
• Biliary enzymes

Question 5

Alanine aminotransferase (ALT)
-found where
-sensitive to what
-only used in…

Answer 5

-found in cytosol/cytoplasm of hepatocytes
-mostly liver spcific
-sensitive to degenerative changes which result in ^ALT
-only used in small animals

Question 6

What is a problem with liver enzymes that causes difficulty to examine liver function

Answer 6

Elevated enzymes do not correlate well with liver function- can have elevated enzymes suggesting marked liver damage but the liver is still functioning adequately.

Question 7

Aspartate aminotransferase (AST)
-found where

Answer 7

-found in cytoplasm of hepatocytes,also has mitochondrial isoenzyme
-also found in skeletal,cardiac muscle and erythrocytes
I.e AST levels can be elevated in animals with or without liver disease; ^ could be caused by other tissues

Question 8

Sorbitol dehydrogenase (SDH)
-found where
-useful in what animals
-disadvantage of it

Answer 8

-found in cytosol of hepatocytes
-useful in horses and cattle
-few labs offer this test as its unstable in vitro; breaks down quite quickly

Question 9

Glutamate dehydrogenase (GLDH)
-found where
-what makes it better than SDH
-useful in what animals

Answer 9

-Found in cytosol of hepatocytes
-Sensitive marker for hepatic injury,but unlike SDH doesn’t break down fast in vitro so easier to use in lab
-useful in horses and cattle

Question 10

Name the biliary enzymes (membrane bound enzymes)

Answer 10

• Alkaline phosphatase (ALP)
• Gamma glutamyl transferase (GGT)

Question 11

What do the biliary enzymes give us an idea about

Answer 11

The biliary tree (bile ducts)

Question 12

Alkaline phosphotase (ALP)
-found where
-what type of enzyme are they

Answer 12

-Found in hepatocytes & biliary epithelial
-isoenzymes- different forms of it: hepatic, intestinal, bone, placental, corticosteroid induced forms

Question 13

^ levels of ALP enzyme indicate…

Answer 13

Cholestasis (impairment of bile flow)
Drug induction e.g corticosteroids
Bone remodelling (bone isoenzyme elevated in the circulation)

Question 14

Gamma glutamyl transferase (GGT)
-found where
-useful. In what animals
-may rise in dogs receiving…
-can be found with ^ levels in urine with what disease?

Answer 14

-Found in biliary system and renal tubules
-useful in cattle, horses and cats
-May rise in dogs receiving corticosteroids
-with renal disease can be found in ^ levels in urine

Question 15

GGT ^ levels indicate what?

Answer 15

Cholestasis

Question 16

Parameters used to assess hepatic function

Answer 16

• Bilirubin (yellow protein that causes jaundice)
• Bile acids
• Albumin and globulin
• Cholesterol
• Urea
• Clotting factors
• Glucose
• Ammonia
• Glucose
• Urinalysis

Question 17

What is hyperbilirubinemia

Answer 17

High levels of bilirubin in circulation

Question 18

Types of hyperbilirubinemia

Answer 18

Prehepatic
Hepatic
Post hepatic

Question 19

Prehepatic hyperbilirubinemia
-what is it
-occurs with what other problem of body

Answer 19

-Amount of bilirubin being produced overwhelms the liver ability to take it on board; make it conjugated. I.e water soluble to then excrete it out of the body.
-Occurs with haemolysis (^ destruction of RBCs)

Question 20

Hepatic hyperbilirubinemia
-when does it occur
-caused by what

Answer 20

-elevation of bilirubin to do with liver
occurs when liver is damaged
-caused by;
—anorexia,
—fasting in horses,
—decreased functional mass (too few heathy functional hepatocytes for uptake, conjugation and excretion of bilirubin),
—intrahepatic Cholestasis (stoppage/ slowing of bile flow)

Question 21

What is Cholestasis

Answer 21

Stoppage, slowing of bile flow

Question 22

Post hepatic hyperbilirubinemia
-what is it
-2 examples

Answer 22

Damage to bile ducts outwith liver
-bile duct tumours
-cholelithiasis

Question 23

What is cholelithiasis

Answer 23

Gall stones that pass out bladder down bile ducts causing blockage in the bile ducts

Question 24

Bile acids
-made of what
-what happens to them
-function
-why is mechanism efficient?

Answer 24

-made by liver from cholesterol
-conjugated and secreted into bile, bile passed out bile ducts into GI tract and it helps digest food.
-function; solubilise lipid, aid fat digestion
-bile acid mechanism very efficient as; most resorbed from intestine and recycled using enterohepatic circulation

Question 25

Describe small animal bile acid testing

Answer 25

-dogs and cats fasted
-blood sample taken
-animal fed
-2 hours later another blood sample taken and serum bile acids measured in both samples

Question 26

During bile acid testing, why are animals fed in between both samples of blood being taken?
What should bile acid sample measurement look like in healthy vs liver diseased patient?

Answer 26

Feeding induces a bonus of bile acids to be released into intestine
-in a healthy patient bile acids should be re absorbed so levels should be low
-patient with disease affecting liver; efficiency reduces and bile acid levels ^.

Question 27

Which animals can’t participate in bile acid testing

Answer 27

Those without a gall bladder e.g horses

Question 28

What causes an increased bile acid content in circulation?

Answer 28

—Portosystemic shunts
-Portal blood bypasses the liver
-Hepatic atrophy resulting from shunt reduces hepatic functional mass
—Liver failure
-Loss of functional mass results in decreased bile acid recycling
—Cholestasis
-Causes reflux of bile acids into blood