3. Liver function and LFTs Flashcards
Functions of the liver?
METABOLIC: Breakdown down carbohydrates, hormones, lipids, drugs and proteins
STORAGE: Glycogen, vitamins, iron
PROTECTIVE: Detoxification and elimination of toxin compounds, kupffer cells ingest bacteria and other foreign material from blood
BILE: Produced and excreted. Formed in biliary canaliculi, emulsifies fats and provides route for waste removal
What two vessels supply the liver and what do they supply it with?
Hepatic artery= Oxygenated blood
Portal vein - Nutrient rick blood
What is the functional unit of the liver and where is it composed of?
Liver lobule:
- Hexagonal in shape
- Hepatocytes arranged in plates
- In contact with bloodstream one one side and bile canaliculi on the other
- Between the plates are vascular spaces (sinusoids) containing Kupffer cells (phagocytic macrophages)
Classifications of liver disease
VAN MIT
Infection- Viral, bacterial, parasitic
Toxic/drug induced
Autoimmune
Biliary tract obstruction- Tumours, gallstones
Vascular
Metabolic : Haemochromatosis, Wilson’s, hereditary hyperbilirubinaemias
Neoplastic
What is cholestasis?
Classifications?
What does it lead to?
Failure to produce or excrete bile
- Intrahepatic = Problems in secretion of bile by hepatocytes due to damage
- Extrahepatic = Problems with flow of bile out of the liver due to obstruction
Result:
- Accumulation of bilirubin in the blood leading to JAUNDICE.
- Urine darkens
- Stool becomes lighter
Other cause for jaundice apart from cholestasis?
Excessive haemolysis, so bilirubin is uncongutated and does not appear in urine
Difference between acute and chronic hepatic failure?
Acute: Development of severe hepatic dysfunction within 24wks of onset of disease
Chronic: Progressive decline in liver function with established disease
What are 3 causes of acute hepatitis?
Poisoning e.g. from paracetamol
Infection (Hepatitis A-C)
Inadequate perfusion
3 potential outcomes for acute hepatitis?
Resolution
Progression to acute hepatic failure
Progression to chronic hepatic damage
3 common and uncommon causes for chronic liver disease?
Common:
- Alcoholic fatty liver
- Chronic active hepatitis
- Primary biliary cirrhosis
Unusual causes:
- Alpha-1 AT deficiency
- Wilson’s disease
- Haemochromatosis
6 consequences of chronic liver disease
- Cirrhosis
- Portal hypertension
- Ascites
- Renal failure
- Easy bruising due to lack of production of clotting factors
- Oedema as osmotic pressure is reduced
What is cirrhosis?
Irreversibile shrinkage of the liver and fibrosis
What is portal hypertension?
Consequences?
Increased blood pressure in the portal vein leading to:
- Haemorrhage of oesophageal / gastric varices
- Hepatic encephalopathy (detoxifying function bypassed)
- Hypersplenism
- Decreased resistance to infections
What is ascites as a consequence of chronic liver disease?
Accumulation of fluid in the peritoneal cavity
What are the features of liver failure?
Inadequate synthesis of albumin
Inadequate synthesis of clotting factors
Inability to eliminate bilirubin
Inability to eliminate nitrogenous waste
What is hepatic encephalopathy?
Name an example
Poorly defined neuro-psychiatric disorder that occurs when products normally metabolised by the liver accumulate in the systemic circulation.
Ammonia: Decreased liver capacity to synthesize urea and glutamine means the ammonia is no longer adequately metabolised and accumulates in the systemic circulation
What 4 Liver Function Tests are done to test if liver disease is present?
- Aminotransferases: ALT and AST for liver cell damage
- Bilirubin- For cholestasis (suggesting bile flow blockage)
- ALP and gamma-GT for biliary epithelial damage and obstruction
- Albumin for synthetic function
What is albumin?
What’s is its relevance in liver function tests?
Albumin is a main plasma protein
Used as an assessment of liver synthetic function but low albumin also found in the following:
- Post surgical/ITU patients due to redistribution
- Significant malnutrition
- Nephrotic syndrome
What is bilirubin?
Breakdown product of haemoglobin
What happens to unconjugated bilirubin?
Taken up by the liver and then conjugated. This can then be excreted in bile.
It is then attacked by bacteria in the colon and excreted in faeces.
Small amounts are reabsorbed and excreted in urine as urobilinogen
Name 4 of the liver enzymes that are used in Liver Function Tests?
AST and ALT
Bilirubin
ALP
gamma-GT
NOT EXCLUSIVELY FOUND IN LIVER TISSUE
What do AST and ALP levels suggest in Liver Function Tests?
These are non-specific markers of acute damage to hepatocytes
What does ALP levels suggest in Liver Function Tests?
Increase in liver disease due to increased synthesis in response to cholestasis
What does gamma-GT levels suggest in Liver Function Tests?
Raised in colestasis, also affected by ingestion of alcohol and drugs such as phenytoin
