Liver function tests Flashcards
Describe the stages of bilirubin metabolism.
1) Pre-hepatic: breakdown of haemoglobin to haem and globin; haem converted to bilirubin and released into the circulation
2) Hepatic: uptake and conjugation of bilirubin in hepatocytes; excretion of conjugated bilirubin into the biliary system
3) Post-hepatic: breakdown of conjugate in the intestines and resorption of bilirubin
Elevated bilirubin can indicate…
1) Pre-hepatic: haemolysis
2) Hepatic: parenchymal damage
3) Post-hepatic: obstruction
What does AST:ALT tell you?
If this is greater than 2:1 –> alcoholic liver disease.
What are the aminotransferases?
AST and ALT are enzymes that are usually found inside hepatocytes. Presence in the blood suggests liver damage.
What is elevated ALP indicative of?
Damage to bile ducts. However, also produced by the placenta during pregnancy.
What is gamma GT?
A non-specific liver enzyme that can become elevated due to a variety of reasons, including NSAID use. Used toconfirm liver source of ALP and can become elevated with alcohol use.
What is albumin tested for?
Synthetic function of the liver. Low albumin? Suggests chronic liver disease - low in kidney disorders and malnutrition.
What is the importance of albumin in the blood?
Exerts an osmotic pressure ie keeps water inside blood vessels. Low levels cause oedema.
What does prothrombin time measure?
Measures how long it takes blood to clot - tells the degree of liver dysfunction. Very important - determines who needs a transplant and who gets a transplant.
Why is creatinine measured?
Tells you about kidney function which determines survival from liver disease.
What does platelet count tell you?
Liver is an important source of thrombopoietin (precursor of platelets). Cirrhosis causes splenomegaly - spleen enlarges then chews up platelets.
Indirect marker of portal hypertension.
