Investigation of jaundice

Jaundice is the result of accumulation of bilirubin in plasma, sometimes from its overproduction but more usually through failure of the liver to either remove it from plasma or excrete it into the intestine via the bile ducts. Bilirubin is a breakdown product of haemoglobin from senescent erythrocytes and circulates tightly bound to albumin before being extracted by hepatocytes and conjugated with glucuronic acid to render it water-soluble for biliary excretion. Overproduction (haemolysis) or reduced conjugation through a defective UDP-glucuronyl transferase in Gilbert’s syndrome results in modest elevations of unconjugated bilirubin (< 100 μmol/l) and absent bile in urine. Congenital absence of the enzyme is seen in Crigler-Najjar syndrome and usually results in deep jaundice, kernicterus and death in infancy. Liver disease and extrahepatic obstruction result in conjugated jaundice with dark urine.With modern imaging, initially transabdominal ultrasound, it is usually possible to identify extrahepatic obstruction, particularly from malignancy, but bile duct stones may be difficult to visualize and may not cause much duct dilatation. Spiral computed tomography, endoscopic ultrasound and magnetic resonance scanning with computerised reconstruction of the cholangiogram (MRC) almost always resolve uncertainties about extrahepatic obstruction. The more invasive endoscopic retrograde cholangiography (ERC) can be reserved for therapeutic interventions such as sphincterotomy and removal of bile duct stones.