Liver Function Tests Flashcards
Although Liver Function Tests are known as “function” tests, what tests are more telling of liver function and not just biochemistry?
- Prothrombin time
- serum albumin
In what 3 states is hypoalbuminaemia seen?
- hypercatabolic states (e.g. chronic inflammation, sepsis)
- excessive renal (e.g. nephrotic syndrome) loss of albumin
- excessive intestinal loss of albumin (intestinal problems with protein loss)
What might cause a prolonged prothrombin time?
biliary obstruction due to vitamin K deficiency because vitamin K is poorly absorbed w/o bile salts
What are the 4 components tested in the LFTs?
- bilirubin
- Aminotransferases (Aspartate aminotransferase and alanine aminotransferase)
- Alkaline phosphatase
- y-GT (glutamyl transpeptidase)
What is bilirubin?
Breakdown product of haemoglobin
What is an isolated rise in bilirubin with normal results in LFTs indicative of?
- inherited problem metabolising bilirubin
- inherited haemolysis problems
- inherited erythropoiesis problems (premature death of red blood cell in bone marrow)
What is Gilbert’s disease?
Inherited problem with metabolising bilirubin leading to increased bilirubin levels in blood leading to jaundice
What is most common cause of hyperbilirubinaemia along with other abnormal LFT results?
biliary tract obstruction
What are aminotransferases and when are they raised?
Enzymes in hepatocytes that leak into blood when hepatocytes are injured
Very low aminotransferase levels may be found in acute hepatitis. True or false?
False
Which aminotransferase is also found in heart and skeletal muscle and so can be raised in M.I./skeletal muscle damage?
Aspartate aminotransferase (AST) -> S-> Skeletal muscle
Which aminotransferase is more specific to the liver?
ALT
Where is alkaline phosphatase situated in the liver?
Canicular and sinusoidal membranes (canicular membranes line the bile canaliculus which is a thin tube that collects bile from hepatocytes and empties it into the common hepatic duct)
What GI related disease can cause raised serum alkaline phosphatase?
Cholestasis (i.e. bile flow obstructed due to impaired hepatocyte secretion or bile duct obstruction)
What are 5 non-GI related reasons for raised alkaline phosphatase levels and why?
- pregnancy
- osteomalacia
- growing children
- Paget’s disease (problem with normal bone tissue recycling process)
- bony metastases
WHY?
alkaline phosphatase also found in bones and placenta
What other measurement can you use to determine whether raised alkaline phosphatase levels are a result of bone/liver disease?
y-GT serum levels
What is y-GT?
liver enzyme
Which enzyme is first to show up in high levels in bile duct obstruction?
y-GT (AKA GGT)
What may induce y-GT and cause it to be raised?
- alcohol
- enzyme-inducing drugs e.g. phenytoin (med used to treat epilepsy)
What is high y-GT a useful screen for?
alcohol abuse
What 2 liver enzymes in high levels together indicate cholestasis?
alkaline phosphatase and GGT
What are 3 cholestatic disorders that can lead to raised serum alkaline phosphatase and raised serum bilirubin in excess of the liver enzymes?
- primary biliary cirrhosis
- primary sclerosing cholangitis
- extrahepatic bile duct obstruction
What is albumin’s function?
- maintains intra-vascular oncotic pressure
- transports water-insoluble substances such as bilirubin and some drugs
