Astavalence

PathoSchema® by Astavalence · Jaundice Simulator

Bilirubin model

31µmol/L

Mild visible jaundice territory.

Bilirubin pathway Jaundice appears when bilirubin production, liver handling or bile drainage overwhelms the system.

Current mechanism

Jaundice overview

Bilirubin is made from haem breakdown, carried to the liver, conjugated by hepatocytes, secreted into bile and excreted through the gut. Jaundice happens when this flow is overloaded or blocked.

Haem breakdown38% Liver processing72% Bile duct obstruction18%

Particle code

Haem breakdownRBC to bilirubin load

Unconjugated bilirubinalbumin bound, not in urine

Conjugated bilirubinwater soluble

Bile flowduct to gut

Dark urineconjugated spillover

Obstruction signalcholestasis pattern

What students must read from the picture

Core rule

Classify jaundice by where the bilirubin pathway fails. Too much production gives mainly unconjugated bilirubin. Hepatocyte disease gives a mixed picture. Bile duct obstruction gives conjugated bilirubin, dark urine, pale stool and cholestatic enzymes.

Clinical reasoning

Mechanism note

Use the sliders. Increase haem breakdown for prehepatic jaundice. Reduce liver processing for hepatocellular jaundice. Increase obstruction for cholestatic jaundice.

Pattern map

Prehepaticmainly unconjugated, haemolysis clues, no bilirubinuria

Hepatocellularmixed bilirubin, high ALT or AST, systemic liver symptoms

Obstructiveconjugated bilirubin, high ALP and GGT, dark urine and pale stool

Urine cluebilirubin in urine means conjugated bilirubin is present

Stool cluepale stool means bile pigment is not reaching the bowel

Pruritusbile salt retention often points towards cholestasis

Exam pearls

Unconjugatednot water soluble, albumin bound, absent from urine

Conjugatedwater soluble, can darken urine

ALP and GGTcholestatic or obstructive pattern

ALT and ASThepatocyte injury pattern

Haemolysis screenFBC, reticulocytes, LDH, haptoglobin and DAT

Imaging firstultrasound is the usual first test for suspected obstruction

Rule: yellow eyes reveal bilirubin. Urine and stool reveal whether bilirubin has been conjugated and whether bile reaches the gut.

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