Jaundice
Jaundice is the yellowing of skin, sclera and mucous membranes, typically seen when bilirubin levels are > 35 µmol/L. There are 3 types of it: Pre-hepatic, Hepatic, Post-hepatic.
Pre-hepatic
This causes an unconjugated hyperbilirubinaemia, which is not water-soluble so doesn't enter the urine. Causes of this include:
Haemolysis e.g. Sickle-cell anaemia, Transfusion reaction
Conjugation disorders e.g. Gilbert’s disease, Crigler-Najjar
Drugs e.g. contrast, rifampicin
Hepatic
With this, there's hepatocellular dysfunction, leading to less conjugation. But, in cirrhotic livers, there’ll also be some obstruction. Overall, both lead to a mixed picture of both unconjugated and conjugated hyperbilirubinaemia. Causes of this include:
Alcohol
Viral infection (Hepatitis, CMV, EBV)
NAFLD
Drugs e.g. paracetamol OD
Autoimmune liver disorders
Liver mass (abscess or malignancy)
Post-hepatic
With this, there's an obstruction of biliary drainage, leading to conjugated hyperbilirubinaemia, which is water-soluble so enters the urine, but doesn't pass into the gut (no stercobilin or urobilinogen production). Therefore, alongside jaundice, patients also present with dark urine (more bilirubin in urine), pale stools (less bilirubin in stool), itchiness. Causes of this include:
Intra-mural - Gallstones, Drug-induced cholestasis (co-amoxiclav, flucloxacillin, steroids, sulfonylureas)
Mural - Cholangiocarcinoma, Strictures, Biliary atresia
Extra-mural - Pancreatic cancer, Abdominal mass
N.B. The deposition of Bile salts in the skin causes the pruritus/itchiness.
Investigations
LFTs - Conjugated and unconjugated bilirubin levels
Amylase (pancreatitis)
Haemolytic screen
Interpretation of LFTs:
Albumin - marker of liver function
AST and ALT - markers of hepatocellular injury (enzymes leak from damaged cells)
ALP - raised in biliary obstruction as well as bone disease (e.g. pagets), pregnancy, and certain cancers
GGT - used after a raised ALP is found as it's more specific for biliary obstruction (confirms an obstruction)