Bilirubin
January 20th, 2018
Overview
Bilirubin is a breakdown product of haem that is conjugated in hepatocytes with glucuronic acid and then excreted in bile.
Normal Range
- Total bilirubin - <1 mg/dL or <20 μmol/L
- Direct (conjugated) bilirubin - <0.3 mg/dL or <7 μmol/L
Significance
- Haemolysis results in unconjugated (indirect) hyperbilirubinaemia, as free haemoglobin is metabolised to haem and then bilirubin.
Causes of Elevated Bilirubin
Unconjugated (Indirect)
- 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
Unconjugated /Conjugated
- 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
Conjugated (Direct)
- 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
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