- Bilirubin is a breakdown product of haem that is conjugated in hepatocytes with glucuronic acid and then excreted in bile.
- Total bilirubin - <1 mg/dL or <20 μmol/L
- Direct (conjugated) bilirubin - <0.3 mg/dL or <7 μmol/L
- Causes of hyperbilirubinaemia can be broken into prehepatic (which tend to cause unconjugated hyperbilirubinaemia), intrahepatic (which may cause either unconjugated or conjugated hyperbilirubinaemia) and posthepatic (which tend to cause unconjugated hyperbilirubinaemia).
Causes of Elevated Bilirubin
- Haemolysis - immune, thrombotic microangiopathy, mechanical, inherited, infection, hypersplenism, drugs
- Haematoma resorption
- Drugs - choramphenicol, probenecid, irinotecan
- Neonatal - neonatal jaundice, jaundice of prematurity
- Inherited conjugation disorders - Gilbert syndrome, Crigler-Najar syndrome
- Acute hepatitis - viral hepatitis, HSV, EBV, CMV, VZV, alcoholic hepatitis, drug-induced hepatitis, ischaemic hepatitis, autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, Wilson’s disease
- Cirrhosis - chronic hepatitis B or C, alcoholic liver disease, non-alcoholic fatty liver disease, autoimmune hepatitis, primary biliary cirrhosis, chronic bile duct obstruction, primary sclerosing cholangitis, haemochromatosis, Wilson’s disease, alpha-1 antitrypsin deficiency, hepatocellular carcinoma, sarcoidosis, glycogen storage disease type IV, methotrexate, methyldopa, amiodarone, Budd-Chiari syndrome, right heart failure
- Intrahepatic cholestasis - primary biliary cirrhosis, primary sclerosing cholangitis, sepsis, HCC, liver metastases, cystic liver disease, intrahepatic cholestasis of pregnancy, cystic fibrosis, total parenteral nutrition, viral / alcoholic hepatitis, amyloidosis, sarcoidosis, augmentin, isoniazid, rifampicin, chlorpromazine
- Extrahepatic cholestasis - choledocholithiasis, bile duct stenosis, bile duct strictures, primary sclerosing cholangitis, bile duct / ampullary / pancreatic malignancy
- Inherited secretion disorders - Dubin-Johnson syndrome, Rotor’s syndrome