Hepatic jaundice from hepatocellular damage
Hepatic jaundice is jaundice from hepatocellular damage, meaning injury to the liver cells (hepatocytes) themselves.
Remember
In jaundice from liver cell damage the bilirubin is mixed and ALT and AST (alanine and aspartate transaminases), the enzymes that leak from injured cells, are the ones that rise, while ALP (alkaline phosphatase), a marker of bile duct damage, stays normal or only mildly raised.
Memory aid
Liver cells leak, bile pipes block
ALT and AST rise when cells leak, and ALP rises when the pipes block.
Jaundice is a yellow discolouration of the skin and of the whites of the eyes. It follows a raised level of bilirubin in the blood, the pigment that is released as haemoglobin is broken down.
Unconjugated bilirubin is not water-soluble. Healthy hepatocytes (liver cells) take it up and conjugate it by attaching glucuronic acid, which makes it water-soluble, and then pass it into bile. Conjugated bilirubin is bilirubin that the liver has made water-soluble.
When the hepatocytes are damaged, both conjugation and passing bilirubin into bile suffer, so unconjugated and conjugated bilirubin accumulate together, which is called a mixed picture. Causes include infection such as acute viral hepatitis (inflammation of the liver caused by a virus), drug toxicity such as paracetamol overdose, and the chronic injury that leads to cirrhosis.
Hepatocytes that are injured let their enzymes leak into the blood, so ALT and AST, the alanine and aspartate transaminases, are raised. Because bile flow is not blocked, ALP (alkaline phosphatase), a marker of bile duct damage, is normal or only mildly raised.
Conjugated bilirubin is water-soluble, so the excess is filtered into the urine, which can make the urine dark. Bile still reaches the gut, so stool colour usually stays normal.
In pre-hepatic jaundice (before the liver), the cause is a blood problem such as haemolysis (red cell breakdown), with mainly unconjugated bilirubin and normal liver tests. In post-hepatic (obstructive) jaundice (after the liver), a blocked duct gives mainly conjugated bilirubin and a markedly raised ALP and GGT (gamma-glutamyl transferase, another marker of bile duct damage).
Key facts
- Bilirubin
- unconjugated and conjugated bilirubin both rise, which makes the pathology likely to be in the liver.
- Enzymes
- ALT and AST are raised, but ALP is normal or only mildly raised.
- Urine
- may be dark, because the excess conjugated bilirubin is filtered into the urine.
- Stools
- usually stay a normal colour, because bile pigment still reaches the gut.
- Causes
- cirrhosis, infection or drug toxicity such as paracetamol overdose.
- Enzyme rule
- ALT and AST point to liver cell damage, while ALP and GGT point to bile duct damage.
Exam traps
- Cholestasis (reduced bile flow) from injury to the cells lining the bile ducts mainly raises ALP and GGT, while ALT and AST show only a modest rise, so it does not give the ALT and AST predominant pattern of liver cell damage.
- Dark urine is shared by hepatic and obstructive jaundice, but pale stools, which appear when bile is blocked from reaching the bowel, suggest obstruction rather than liver cell damage, and obstruction also gives a markedly raised ALP and GGT.
- Raised ALT and AST with a normal ALP show liver cell injury, but if the bilirubin is normal the person is not jaundiced, so a normal bilirubin is not hepatic jaundice.
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