Page 189 - Medicine and Surgery

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Chapter 5: Clinical 185

Jaundice Prehepatic jaundice results from excess bilirubin pro-
duction (e.g. haemolytic anaemia) or abnormalities in
Definition
bilirubin conjugation such as occur in some forms
Yellow pigmentation to the sclera and skin, it is clini-
of congenital hyperbilirubinaemia (Gilbert’s syndrome
cally evident when the plasma bilirubin level is above
and Crigler–Najjar syndrome). The mildly raised serum
50 mcmol/L (2.5 mg/dL).
bilirubin is unconjugated and other liver function tests
are normal.
Aetiology/pathophysiology Hepaticjaundiceresultsfromhepatocytedamagewith
Jaundice is due to an abnormality in the metabolism or without intrahepatic cholestasis. Causes include hep-
or excretion of bilirubin, which is derived from haem atitis of any cause, cirrhosis, drugs, liver metastases, sep-
containing proteins such as haemoglobin. sis, other liver diseases and some forms of congenital
Unconjugated (water insoluble) bilirubin is trans- hyperbilirubinaemia (Dubin–Johnson syndrome and
ported to the liver bound to albumin. It is taken up by Rotor syndrome). There is raised conjugated and un-
hepatocytes and conjugated in a two-stage process to a conjugated bilirubin, and often liver function tests are
watersolubleform.Bilecontainingconjugatedbilirubin, abnormal due to hepatocyte damage (see page 189).
bile salts, cholesterol, phospholipids and electrolytes is Posthepatic jaundice results from obstruction of the
secreted into the intrahepatic bile ducts and passes to biliary tree distal to the bile canaliculi of the liver. Causes
the gallbladder via the common hepatic duct where it is include gallstones in the common bile duct, pancreatic
stored. Gallbladder contraction (e.g. following a meal) cancer, cholangiocarcinoma, primary biliary cirrhosis
causes bile to pass via the cystic duct into the common andprimarysclerosingcholangitis.Thereisaconjugated
bile duct and hence into the duodenum through the am- hyperbilirubinaemia with increased urinary excretion of
pulla of Vater (see Fig. 5.1). water-soluble conjugated bilirubin. If there is complete

Red cell breakdown

Haemoglobin split Globin Haem

Bilirubin binds to albumin Iron Bilirubin
(unconjugated)

Conjugation
Biliary tree
Hepatocyte uptake and conjugation

Storage in gallbladder
Ampulla of Vater
Secretion into duodenum

Enterohepatic
90–95% reabsorption at the terminal ileum circulation
5–10% excretion in stool (stercobilin) and urine (urobilinogen)

Figure 5.1 Bilirubin metabolism.