Overview
Classify jaundice by bilirubin and liver-enzyme pattern, recognise cholangitis and liver failure, investigate obstruction without delay, and treat cholestatic itch while the underlying hepatobiliary disease is established.
Jaundice becomes visible when bilirubin accumulates, but the route to diagnosis is pattern based. Unconjugated bilirubin rises with increased production, impaired uptake or conjugation, as in haemolysis or Gilbert syndrome, and is not excreted in urine. Conjugated bilirubin is water soluble and darkens urine when hepatocytes cannot excrete it normally or bile flow is blocked. Compare ALT and AST with alkaline phosphatase, using GGT or isoenzymes when the ALP source is uncertain. A cholestatic pattern suggests duct obstruction, drug injury, sepsis or autoimmune cholangiopathy; a hepatocellular pattern suggests viral, drug, ischaemic, autoimmune or metabolic injury. Mixed patterns require equal breadth.
History gives the urgency. Fever and pain suggest infected obstruction; painless progression and weight loss raise pancreatic, ampullary or cholangiocarcinoma; very high aminotransferases after hypotension, overdose or viral prodrome raises acute hepatocellular injury. Ask about prescribed and non-prescribed medicines, paracetamol timing, alcohol, travel, tattoos, injections, sexual and occupational exposure, pregnancy, surgery and family disease. Examine mental state, perfusion, scratching, xanthelasma, bruising, nodes, liver and spleen, ascites and a palpable gallbladder. Asterixis, hypoglycaemia and new coagulopathy indicate failing synthesis and detoxification rather than merely abnormal enzymes.