Liver Function Test Flashcards
What are the classifications of liver disease
- Infection (Viral, bacterial, parasitic)
- Toxic/drug induced
- Autoimmune
- Biliary tract obstruction
- Vascular
- Metabolic
- Neoplastic
Causes of acute hepatitis
- Poisoning (paracetamol)
- Infection (Hep A-C)
- Inadequate perfusion
Outcome of acute hepatitis
- Resolution in majority of cases
- Progression to acute hepatic failure
- Progression to chronic hepatic damage
Common causes of chronic liver disease
- Alcoholic fatty liver
- Chronic active hepatitis
- Primary biliary cirrhosis
Unusual causes of chronic liver disease
- a-1 AT deficiency
- Haemochromatosis
- Wilson’s disease
Define cholestasis
Failure to produce/excrete bile
Result of cholestasis
Accumulation of conjugated bilirubin in the blood, leading to jaundice
What does liver failure result in
- Inadequate synthesis of albumin, leading to oedema and ascites
- Inadequate synthesis of clotting factors, resulting in bruising
- Inability to eliminate bilirubin, causing jaundice
- Inability to eliminate nitrogenous waste (e.g. ammonia) giving rise to hepatic encephalopathy
What do current liver function tests cover
- Albumin
- ALT (+ AST)
- ALP (+ gamma-GT)
- Bilirubin
Why measure albumin
Synthetic function
Why measure ALT
Aminotransferases for hepatocellular damage
Why measure ALP
For biliary epithelial damage and obstruction
Why measure bilirubin
For cholestasis
Advantages of current liver function tests
- Cheap, widely available, interpretable
- Able to direct next subsequent investigation (e.g. imaging)
Disadvantages of current liver function tests
- Does not assess liver function
- Lack of complete organ specificity
- Lack of disease specificity
- May be over-sensitive
Where else is low albumin found
- Post-surgical/ITU patients due to redistribution
- Significant malnutrition
- Nephrotic syndrome
When is ALP raised
- In liver disease due to increased synthesis
- In response to cholestasis
When is gamma-GT raised
- Cholestasis
- Affected by ingestion of alcohol/drugs such as phenytoin
Where else is ALP present
- Bone
- Gut
- Placenta
Where else is gamma-GT present
- Bone
- Biliary tract
- Pancreas
- Kidney
What happens to bilirubin once excreted in bile
- Attacked by bacteria in colon and excreted in faeces
- Small amounts reabsorbed and excreted in urine as urobilirubin
What can cause cholestasis
- Failure by hepatocytes (intrahepatic cholestasis)
- Obstruction to bile flow (extra hepatic obstruction)
What does an increased est ALT/ALP, normal ALT and increased ALP suggest
Cholestasis
What does an increased est ALT/ALP and >10 fold increase in ALT and decrease in ALP suggest
Hepatocellular
