Clinical Pathology Of The Liver Flashcards
Functions of the liver
• 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
Name the hepatocellular (liver) enzymes
• Alanine aminotransferase (ALT)
• Aspartate aminotransferase (AST)
• Sorbitol dehydrogenase (SDH)
• Glutamate dehydrogenase (GLDH)
Which 2 types of tube sampling are used for testing the liver
Serum or lithium heparin sample
Parameters used investigate liver damage
• Hepatocellular enzymes
• Biliary enzymes
Alanine aminotransferase (ALT)
-found where
-sensitive to what
-only used in…
-found in cytosol/cytoplasm of hepatocytes
-mostly liver spcific
-sensitive to degenerative changes which result in ^ALT
-only used in small animals
What is a problem with liver enzymes that causes difficulty to examine liver function
Elevated enzymes do not correlate well with liver function- can have elevated enzymes suggesting marked liver damage but the liver is still functioning adequately.
Aspartate aminotransferase (AST)
-found where
-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
Sorbitol dehydrogenase (SDH)
-found where
-useful in what animals
-disadvantage of it
-found in cytosol of hepatocytes
-useful in horses and cattle
-few labs offer this test as its unstable in vitro; breaks down quite quickly
Glutamate dehydrogenase (GLDH)
-found where
-what makes it better than SDH
-useful in what animals
-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
Name the biliary enzymes (membrane bound enzymes)
• Alkaline phosphatase (ALP)
• Gamma glutamyl transferase (GGT)
What do the biliary enzymes give us an idea about
The biliary tree (bile ducts)
Alkaline phosphotase (ALP)
-found where
-what type of enzyme are they
-Found in hepatocytes & biliary epithelial
-isoenzymes- different forms of it: hepatic, intestinal, bone, placental, corticosteroid induced forms
^ levels of ALP enzyme indicate…
Cholestasis (impairment of bile flow)
Drug induction e.g corticosteroids
Bone remodelling (bone isoenzyme elevated in the circulation)
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?
-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
GGT ^ levels indicate what?
Cholestasis
Parameters used to assess hepatic function
• Bilirubin (yellow protein that causes jaundice)
• Bile acids
• Albumin and globulin
• Cholesterol
• Urea
• Clotting factors
• Glucose
• Ammonia
• Glucose
• Urinalysis
What is hyperbilirubinemia
High levels of bilirubin in circulation
Types of hyperbilirubinemia
Prehepatic
Hepatic
Post hepatic
Prehepatic hyperbilirubinemia
-what is it
-occurs with what other problem of body
-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)
Hepatic hyperbilirubinemia
-when does it occur
-caused by what
-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)
What is Cholestasis
Stoppage, slowing of bile flow
Post hepatic hyperbilirubinemia
-what is it
-2 examples
Damage to bile ducts outwith liver
-bile duct tumours
-cholelithiasis
What is cholelithiasis
Gall stones that pass out bladder down bile ducts causing blockage in the bile ducts
Bile acids
-made of what
-what happens to them
-function
-why is mechanism efficient?
-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
