pathophysiology of jaundice, definition , cause

1. JAUNDICE
By: Ms. Harsha Ashtekar Asst. Lecturer
Dept. : Pharmacology
Sub. : pathophysiology
Maratha Mandal’s College Of Pharmacy , Belgaum.

2. DEFINITION
• Excess of bilirubin or hyperbilirubinaemia causes an important clinical
condition called jaundice.
• Hyperbilirubinaemia may be unconjugated or conjugated, and jaundice
may appear in one of the following 3 ways:
• a) Prehepatic or haemolytic, when there is excessive destruction of red
cells.
• b) Posthepatic or obstructive, which results from obstruction to the
outflow of conjugated bilirubin.
• c) Hepatocellular that results from failure of hepatocytes to conjugate
bilirubin and inability of bilirubin to pass from the liver to intestine.

3. • Jaundice or icterus refers to the yellow pigmentation of the skin or
sclerae by bilirubin.
• ilirubin pigment has high affinity for elastic tissue and hence jaundice
is particularly noticeable in tissues rich in elastin content.
• Jaundice is the result of elevated levels of bilirubin in the blood
termed hyperbilirubinaemia.
• Normal serum bilirubin concentration ranges from 0.3-1.3 mg/dl,
about 80% of which is unconjugated. Jaundice becomes clinically
evident when the total serum bilirubin exceeds 2 mg/dl.

4. NORMAL BILIRUBIN METABOLISM
• Normal metabolism of bilirubin can be conveniently described under
4 main headings—source, transport, hepatic phase and intestinal
phase
• SOURCE OF BILIRUBIN. About 80-85% of the bilirubin is derived from
the catabolism of haemoglobin present in senescent red blood cells
• The remaining 15-20% of the bilirubin comes partly from non-
haemoglobin haemcontaining pigments such as myoglobin, catalase
and cytochromes, and partly from ineffective erythropoiesis. Bilirubin
is formed from biliverdin by biliverdin reductase.

5. • TRANSPORT OF BILIRUBIN. Bilirubin on release from macrophages
circulates as unconjugated bilirubin in plasma tightly bound to
albumin. Bilirubin is found in body fluids in proportion to their
albumin content such as in CSF, joint effusions, cysts etc.
• HEPATIC PHASE. On coming in contact with the hepatocyte surface,
unconjugated bilirubin is preferentially metabolised which involves 3
steps: hepatic uptake, conjugation and secretion in bile.
• INTESTINAL PHASE. Appearance of conjugated bilirubin in the
intestinal lumen is followed by either direct excretion in the stool as
stercobilinogen which imparts the normal yellow colour to stool, or
may be metabolised to urobilinogen by the action of intestinal
bacteria

6. CLASSIFICATION AND FEATURES OF JAUNDICE
• Based on pathophysiology, jaundice may result from one or more of
the following mechanisms:
1. Increased bilirubin production
2. Decreased hepatic uptake
3. Decreased hepatic conjugation
4. Decreased excretion of bilirubin into bile

7. Pathophysiological classification
• PREDOMINANTLY UNCONJUGATED HYPERBILIRUBINAEMIA
1. Increased bilirubin production (Haemolytic, acholuric or prehepatic jaundice)
• Intra- and extravascular haemolysis
• Ineffective erythropoiesis
2. Decreased hepatic uptake
• Drugs
• Prolonged starvation
• Sepsis
3. Decreased bilirubin conjugation
• Hereditary disorders (e.g. Gilbert’s syndrome, Crigler-Najjar syndrome)
• Acquired defects (e.g. drugs, hepatitis, cirrhosis)
• Neonatal jaundice

8. • PREDOMINANTLY CONJUGATED HYPERBILIRUBINAEMIA (CHOLESTASIS)
1. Intrahepatic cholestasis (Impaired hepatic excretion)
• Hereditary disorders or ‘pure cholestasis’ (e.g. Dubin-Johnson syndrome,
Rotor’s syndrome, fibrocystic disease of pancreas, benign familial recurrent
cholestasis, intrahepatic atresia, cholestatic jaundice of pregnancy)
• Acquired disorders or ‘hepatocellular cholestasis’ (e.g. viral hepatitis,
drugs, alcohol-induced injury, sepsis, cirrhosis)
2. Extrahepatic cholestasis (Extrahepatic biliary obstruction)
• Mechanical obstruction (e.g. gallstones, inflammatory strictures, carcinoma
head of pancreas, tumours of bile ducts, sclerosing cholangitis, congenital
atresia of extrahepatic ducts)