Liver Function and LFTs Flashcards
What are the causes of acute hepatitis?
- poisoning (paracetamol)
- infection (hepatitis)
- inadequate perfusion
What are the common causes of chronic liver disease?
- alcoholic fatty liver
- chronic active hepatitis
- primary biliary cirrhosis
What is cholestasis and the types?
a consequence of the failure to produce or excrete bile
- failure by hepatocytes: intrahepatic cholestasis
- obstruction to bile flow: extrahepatic cholestasis
What is the result of cholestasis?
accumulation of bilirubin in blood causing jaundice
What are the consequences of liver failure?
- inadequate synthesis of albumin leading to oedema and ascites
- inadequate synthesis of clotting factors causing bruising
- inability to eliminate bilirubin causing jaundice
- inability to eliminate nitrogenous waste, giving rise to encephalopathy
What are the components of an LFT panel?
- albumin
- ALT (and AST) (enzymes)
- ALP (alkaline phosphatase)
- (γgT)
- bilirubin
What are the pros and cons of using albumin levels as an assessment of liver function?
Pros:
- main plasma protein produced by liver
- good for assessment of livers synthetic function
Cons: low albumin also found in - post surgical/ITU patients due to redistribution - significant malnutrition - nephrotic syndrome
What are the pros and cons of using ALT and AST levels as an assessment of liver function?
Pros:
- cytoplasmic enzymes which are sensitive markers of acute hepatocyte damage
Cons:
- non specific (enzymes found in other locations of the body as well such as cardiac muscle)
- levels are raised in other conditions such as skeletal muscle disorders and MI
What are the pros and cons of using alkaline phosphatase (ALP) as an assessment of liver function?
Pros:
- used for looking at biliary epithelial damage and obstruction
- increased in liver disease due to increased synthesis in response to cholestasis
Cons:
- ALP also present in other areas (bone, gut, placenta)
It is also raised in:
- physiological state (childhood/pregnancy)
- broken bones/bone disease
- induced by drugs
What are the pros and cons of using γgT as an assessment of liver function?
Pros:
- can be used to look for biliary epithelial damage and obstruction
- super sensitive
Cons:
- also present in other places (bone, biliary tract, pancreas, kidney)
- affected by ingestion of alcohol and drugs like phenytoin
- possibly over-sensitive
What are the pros and cons of using bilirubin as an assessment of liver function?
Pros:
- breakdown product of haemoglobin: unconjugated is taken up by liver, conjugated is excreted in bile
- if raised causes clinical jaundice
- indicator of cholestasis
Cons:
- also raised in haemolysis
- hereditary hyperbilirubinaemias
What are the pros and cons of LFTs?
Pros:
- cheap
- widely available, interpretable
- direct subsequent investigation (eg. imaging)
Cons:
- do not assess liver ‘function’
- lack of organ specificity
- lack disease specificity
- can be oversensitive
Describe what you would see in an LFT of acute hepatocellular damage
- bilirubin: big increase
- ALT: big increase
- Alk Phos: normal or raised
- γGT: normal or raised
Describe what you would see in an LFT of chronic hepatocellular damage
- bilirubin: normal or raised
- ALT: normal or raised
- Alk Phos: normal or raised
- γGT: normal or raised
Describe what you would see in an LFT of cholestasis
- bilirubin: big increase
- ALK: raised
- Alk Phos: big increase
- γGT: big increase
