- Jaundice (French – yellow: icterus - Greek – jaundice). Jaundice is not a disease, it is a sign.
- Jaundice is defined as yellow discolouration of skin, sclerae, mucous membranes and internal organs caused by an increase in bilirubin concentration in tissues. To understand jaundice, it is essential to know the bilirubin production.
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Jaundice - Icteric - Subcutis
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Causes of jaundice
- Overproduction of bilirubin due to increased haemolysis.
- Reduced uptake in liver, impaired conjugation (lack of enzymes)
- Impaired intrahepatic secretion due to hepatic damage, intrahepatic cholestasis due to biliary obstruction
- Impaired extrahepatic secretion due to obstruction - Due to bileduct obstruction.
Jaundice is classified into
- Haemolytic or prehepatic jaundice
- Toxic or intrahepatic jaundice
- Obstructive or posthepatic jaundice
Haemolytic or prehepatic jaundice
- Causes
- Bacteria : Clostridium haemolyticum, Leptospirosis
- Virus : Equine infectious anaemia
- Protozoa : Babesiosis, Anaplasmosis, Haemobartonellosis, Trypanosomosis
- Nutritional : Phosphorus deficiency - Post parturient haemoglobinuria
- Phytotoxins : Resin, Saponin
- Animal toxin : Snake venom
- Chemicals : Copper, selenium toxicity in sheep
- Icterus neonatarum, incompatible blood supply
- Pathogenesis
- Excessive haemolysis results in production of greater amount of unconjugated bilirubin. Since there is a rate limiting, all unconjugated bilirubin cannot be converted to conjugated bilirubin. Hence, some amount is left in the blood. Since large amount of conjugated bilirubin is formed, it stains faeces yellow. When excess quantity of urobilin is formed (faeces intense yellow colour) and is also responsible for abnormal intense yellow urine.
Toxic or intrahepatic jaundice
- Causes
- Bacteria : Leptospirosis, Salmonellosis
- Virus : Infectious canine hepatitis
- Phytotoxins : Senecio, crotalaria
- Chemicals : Phosphorus, chronic copper poisoning, chloroform, carbon tetrachloride.
- Pathogenesis
- When heptocytes are necrosed, the liver is not able to convert normally formed unconjugated bilirubin. Since the degenerated cells are swollen and disorganised and biliary capillaries are blocked, conjugated bilirubin escapes into sinusoids and enters general circulation and excreted through urine. Hence, blood contains both conjugated and unconjugated bilirubin.
Obstructive or posthepatic jaundice
- Causes
- Blocking of bileduct from within
- Ascaris lumbricoides in swine
- Thysanosoma astiniodes (fringed tape worm)
- Fasciola gigantica in cattle
- Gall stones
- Pressure on bile duts from outside
- Tumours, abscesses, granulomas, fibrosis, enlarged pancreas or lymph nodes
- Inflammatory processes in biliary system
- Cholangitis, cholecystitis – fascioliasis, Dicrocoelium dendriticum
- Closure of bile duct orifice in duodenum
- Duodenitis – thickening of mucosa
- Pathogenesis
- The obstruction to normal flow of bile results in regurgitation of bile. In this case, the production of conjugated and unconjugated bilirubin is normal. Biliary stasis occurs due to (extra hepatic cholestasis) pressure, worms, inflammation and duodenitis. No urobilinogen is formed since bile is not entering to intestine. Faeces greasy and grey colour due to failure of fat emulsification and lack of faecal pigment. Urine is not containing urobilin. Clotting defects will occur due to failure of obstruction of vitamin K which is required for prothrombin formation.
Chemical test for bilirubin
van den Bergh test
Differential diagnosis of jaundice
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S.No.
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Parameters
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Haemolytic
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Toxic
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Obstructive
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1.
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Bilirubin
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Increased unconjugated bilirubin
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Increased conjugated and unconjugated bilirubin
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Increased conjugated bilirubin
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2.
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Serum van den Bergh test
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Indirect
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Biphasic
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Direct
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3.
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Urine bilirubin
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Not present
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Present
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Present
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4.
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Urine urobilinogen
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Slightly present
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Present
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Not present
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5.
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Feaces
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Intense yellow, no smell
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Normal
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Clay coloured, greasy, foul smell
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6.
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Liver function tests
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Negative
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Positive
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Negative
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7.
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Blood prothrombin time
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Normal
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Prolonged
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Prolonged
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8.
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Total serum cholesterol
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Normal
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Decreased
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Increased
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9.
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Haemoglobinuria, anaemia and blood parasite
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Present
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Absent
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Absent
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Participants