Liver Function Tests Flashcards
What enzymes are markers of hepatocellular injury
- Aspartate aminotransferase (AST)
- Alanine aminotransaminase (ALT)
ALT and AST levels when there is a viral/toxic liver injury
Serum ALT rises more than serum AST
The higher the ALT to AST ratio, the higher the what?
The higher the likelihood that alcohol is contributing to abnormal LFTs
AST assay reaction (not coupled)
Aspartic Acid + Apha-Ketoglutaric Acid —–> Oxalecetic Acid + Glutamic Acid
(in the presence of AST)
Where is bilirubin conjugated
Liver
What is bilirubin conjugated w
Guluronic acid
What is bilirubin excreted as
- Urobilin in urine
- Stercobilin in faeces
In terms of bilirubin, what does liver disease impair
Secretion of conjugated bilirubin into bile - results in conjugated bilirubin being rapidly filtered into urine
Steps of senescent red cells -> conjugated bilirubin
- Senescent rbcs phagocytosed by macrophages
- Heme broken down to green biliverdin
- By heme oxygenase
- Biliverdin broken down to orange bilirubin
- By biliverdin reductase
- Bilirubin conjugated w glucuronic acid
Acute liver disease causes
- Poisoning - paracetamol
- Infections - Hep A,B,C
- Inadequate Perfusion - physical damage causes reduced blood flow
Markers for acute liver disease
- increased AST
- increased ALT
- both = hepatocellular damage
- increased serum bilirubin
- increased ALP
- both = presence of cholestasis
Outcomes for acute liver disease
- It is resolved
- Progress to acute liver failure
- Leads to chronic liver damage
the 3 forms of liver damage
- alcoholic fatty liver
- chronic active hepatitis
- primary biliary cirrhosis
What is the terminal stage of chronic liver damage
Cirrhosis
3 causes of cirrhosis
- chronic excess alcohol ingestion
- viral hepatitis
- autoimmune disease
Link between CF and cirrhosis
Problems w drainage of bile out of liver via bile ducts & gallbladder - mucous builds up & blocks bile ducts
Problems w scarring of liver -> fibrosis & cirrhosis
Clinical features of terminal stage cirrhosis
- Jaundice
- Encephalopathy
- Ascites
- Bleeding tendencies
- Terminal liver failure
