Bilirubin and Jaundice

Bilirubin and Jaundice

Unconjugated hyperbilirubinaemia

  • Pre-hepatic (acholuric)
  • Hepatocellular

Conjugated hyperbilirubinaemia

  • Hepatocellular
  • Intrahepatic obstruction
  • Extrahepatic obstruction

Note:

  • <20% of bilirubin conjugated = Unconjugated hyperbilirubinaemia
  • >50% of bilirubin conjugated = Conjugated hyperbilirubinaemia

Unconjugated hyperbilirubinaemia

Classification:

  • Pre-hepatic (acholuric) (vast majority. Secondary to increased bilirubin production
  • Hepatocellular. Secondary to reduced hepatocyte uptake of bilirubin.

Cause:

  • Haemolysis (must be 2 x normal to be significant) – Rarely causes rise over 70 micromol/L
    • haemolytic anaemia
    • erythroblastosis foetalis
    • pernicious of prematurity
  • Congenital
    • Gilbert disease (GD)
    • Crigler-Najjar syndrome (CS)
  • Iatrogenic
    • Drugs: chloramphenicol, gentamicin, pregnanediol
  • Physiological
    • Neonatal jaundice and Breast-milk jaundice

Conjugated hyperbilirubinaemia

  • Hepatocellular – Diminished hepatocyte function. If severe can be associated with unconjugated hyperbilirubinemia due to total inability to conjugate bilirubin
    • hepatitis – Viral, toxic, alcoholic, autoimmune
    • cirrhosis
    • leptospirosis
    • Drugs
      • liver parenchymal injury (toxic hepatitis)
      • halothane, paracetamol, methyldopa, phenytoin, barbiturates, MAOI, sulphonamides
  • Intrahepatic obstruction (hepatic canalicular disorders)
    • Hepatitis (viral)
    • Cirrhosis (Primary biliary cirrhosis)
    • Intrahepatic cholestasis
    • Drugs
      • indomethacin, erythromycin
      • chlorpromazine, isoniazid, flucloxacillin, OCP
    • Congenital
      • Dubin–Johnson syndrome
      • Rotor syndrome
  • Extrahepatic obstruction
    • Calculi, tumour, scar tissue in common bile duct or hepatic excretory duct
    • Gallstones, carcinoma of head of pancreas and lymphoma with extrinsic nodal compression of the porta hepatis are commonest

Serum Bilirubin

Measures unconjugated and conjugated (Normal range: 6-24 micromol/L). Initial result details TOTAL bilirubin measured

  • Clinically detectable jaundice
    • Conjugated hyperbilirubinaemia – 35 micromol/L
    • Unconjugated hyperbilirubinaemia – 45 micromol/L
  • Ratio of unconjugated and conjugated helps to determine cause of hyperbilirubinaemia
    • Predominantly unconjugated (<20% bilirubin conjugated)
    • Predominantly conjugated (>50% bilirubin conjugated)

Urine Bilirubin

Ward Test Urine (WTU) or laboratory for may assess urine for Urine bilirubin and Urine urobilinogen

Urine bilirubin:

  • Conjugated bilirubin excreted into GIT is reabsorbed in very small amounts
  • Kidneys filter soluble form and it appears in urine
  • Bilirubin is NOT normally present in urine
  • Urine -dark in colour, usually brown with yellow foam
  • Presence of bilirubin implies Conjugated hyperbilirubinemia

Urine urobilinogen:

  • Normal: 1-4mg/day (compared to 250mg in stool)
  • Absence of urobilinogen
    • Conjugated – Complete extrahepatic obstruction or Broad spectrum antibiotics destroying intestinal flora
  • Low levels of urobilinogen
    • Unconjugated – Congenital (Crigler-Najjar syndrome, Gilbert syndrome)
    • Conjugated – Complete extrahepatic obstruction
  • Increased levels
    • Unconjugated – haemolysis, highly alkaline urine or eating bananas up to 48 hours before test
Bilirubin and Jaundice investigations

CCC 700 6

Critical Care

Compendium

Emergency physician MA (Oxon) MBChB (Edin) FACEM FFSEM with a passion for rugby; medical history; medical education; and informatics. Asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | vocortex |

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.