Liver Function Tests

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  • Created by: Becca
  • Created on: 24-12-13 00:50
What are the main liver function tests?
Bilirubin (-> jaundice), hepatocellular (aminotransferases: ALT/AST), obstruction (alkaline phosphatase: ALP, gamma-glutamyl transpeptidases = gamma GTs), synthetic function (albumin, coagulation: INR)
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How is bilirubin used to test liver function?
Breakdown product of RBCs, biliverdin reduced to bilirubin (unconjugated, H20 insoluble). Liver conjugates bilirubin to make it soluble, excreted as bile, causes jaundice. Increased in obstruction, hepatocellular damage & haemolysis
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How are aminotransferases used to test liver function?
Aspartate (AST)/Alanine (ALT) leak out from damaged cells, raised plasma concentrations in hepatocellular damage. ALT more specific marker of liver damage
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How is alkaline phosphatase used to test liver function?
Present in canalicular & sinusoidal membranes of liver, raised levels in cholestasis & infiltration of liver e.g. metastasis of cancer
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How is gamma GT used to test liver function?
Microsomal enzyme present in many tissues including liver. Increased by induction (alcohol, drugs) seen in cholestasis. May be inreased in cellular damage
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How is albumin used to test liver function?
Measures synthetic activity of liver (function), indicates changes over a longer term as it has a longer half life of 16-24 days
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How is INR used to test liver function?
Prothrombin time indicates synthetic activity (and coagulation). Coagulation factors have a relatively short half life so indicates both acute and chronic damage
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What would the LFTs show for acute hepatitis?
Increased ALT & AST
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What would the LFTs show for cholestasis?
Increase ALP, GGT & bilirubin
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What would the LFTs show for chronic liver disease?
Increased INR & bilirubin. Decreased albumin
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What is prehepatic jaundice? What causes it?
Water insoluble unconjugated bilirubin is produced faster than liver can conjugate it for excretion. Often due to haemolysis - haemolytic anaemias, Gilbert's syndro
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What is hepatocellular jaundice?
Transaminases leak out, liver can't convert insoluble bilirubin from the blood to water soluble bilirubin. Reduced bilirubin excretion results in jaundice, normal or pale stools
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What is cholestasis? What are the 2 types?
Bile can't flow from the liver to the duodenum. Intrahepatic: primary biliary cirrhosis (autoimmune bile duct damage), hepatocellular damage, pregnancy. Extrahepatic: gallstones, carcinoma of head of pancreas -> obstruction/strangulation of bile duct
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What happens in obstructive jaundice? What are the LFT results?
Cholestasis, GGT & ALP not excreted, elevated. Liver can convert insoluble bilirubin but can't excrete it in bile -> pale stools. Water soluble bilirun is excreted in urine -> dark urine
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What are the main complications of liver disease?
Jaundice, ascites (fluid in peritonea cavity due to oedema, Na retention, portal hypertension), encephalopathy (neuropsychiatric), impaired coagulation, gastric bleeding, bleeding oesophageal varices
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Card 2

Front

How is bilirubin used to test liver function?

Back

Breakdown product of RBCs, biliverdin reduced to bilirubin (unconjugated, H20 insoluble). Liver conjugates bilirubin to make it soluble, excreted as bile, causes jaundice. Increased in obstruction, hepatocellular damage & haemolysis

Card 3

Front

How are aminotransferases used to test liver function?

Back

Preview of the front of card 3

Card 4

Front

How is alkaline phosphatase used to test liver function?

Back

Preview of the front of card 4

Card 5

Front

How is gamma GT used to test liver function?

Back

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