Liver Function Flashcards
What is involved in the normal function of the liver?
- Intermediary metabolism
- Xenobiotic metabolism
- Protein synthesis
- Bile synthesis
- Reticulo-endothelial function (immune modulating)
What is intermediary metabolism?
It is an enzyme controlled process that extracts energy and uses it to construct cellular components.
In liver failure, why can a patient become encephalopathic?
There is increased ammonia, which is encephalotoxic
What enzyme is involved in many of the xenobiotic functions of the liver?
Cytochrome P450
What is the function of bile?
- Excretion
- Micelle formation
- Digestion
In a liver function test, what is measured?
Liver cell damage:
- AST and ALT
- AlkPhos
- GGT
- Bilirubin
- AFP
Liver function:
- Clotting factors
- Albumin
- Glucose
What is the function of the aminotransferases?
They are involved in amino acid metabolism
Where can aminotransferases be found? What is the normal level? When can they be raised?
They are predominately found in hepatocytes, but can be found in the muscle, brain and kidneys.
The normal level is less than 40iu/L.
They can be raised in hepatocellular death.
How can the relative levels of the aminotransferases specify the cause of hepatocellular death?
If AST:ALT is >2 this is likely alcoholic.
If it is above this with no alcohol history, it is likely cirrhosis.
If AST:ALT is <1.1, it is likely viral damage.
What is the function of alkaline phosphatase?
This is largely unknown.
What is the normal level of ALP? When can it be raised?
It is normally between 30 and 150 iu/L.
It can be raised in cholestasis and bone disease. It is also raised in pregnancy and malignancy.
What is gamma-glutamyl transferase involved in?
It is involved in amino acid metabolism.
What is the normal level of GGT? When can it be raised?
It is normally between 30 and 150 iu/L.
It is raised in chronic alcohol use. It can also be raised in bile duct disease and metastasis.
What is the role of albumin?
It is primarily involved in controlling the oncotic pressure of blood.
When can albumin levels be low?
- Low production (liver disease)
- Loss of albumin (renal or GI loss)
- Sepsis (capillary leakage)
Why can clotting factors be a better marker than albumin for acute disease?
The half life of clotting factors is much shorter (albumin is 20 days, clotting factors are mere hours) so any change can be detected far closer to a change in pathology.
What is the role of alfa fetoprotein?
It is primarily involved in foetal immune modulation. In adults, its purpose in unclear.
When can alfa fetoprotein be raised?
It is raised in hepatocellular carcinoma, and is a good cancer marker for testicular cancer as well. It is also raised in pregnancy.
In raised bilirubin, what is the best way to consider the pathology involved?
Consider the rest of the liver function test:
Normal hepatic enzymes:
- Haemolysis
- Gilbert’s syndrome
Raised ALP:
- Obstructive jaundice (gall stones, pregnancy)
- Non-obstructive jaundice (PBC, PSC)
Raised AST/ALT:
- Acute or chronic hepatocellular damage
What is the significance of pale stools and dark urine when considering a raised bilirubin?
This shows the jaundice is obstructive, giving this clinical picture.
What is the ‘liver panel’?
These are further tests that can be made when the liver function test is unclear. It involves:
- Hepatitis screen
- CK, TFTs
- Alpha-1-antitrypsin
- Immunoglobulins
In a patient with a raised ALT, what must be considered when discussing management?
You must look at the other markers in the LFTs.
If isolated raised ALT:
- Discuss lifestyle changes
If symptomatic/unisolated raised ALT:
- Conduct liver function tests and liver screen to determine cause
- Treat the cause
