Jaundice

18 Jaundice


Jaundice (icterus) is a relatively common presenting complaint or finding in dogs and cats. This syndrome is characterized by hyperbilirubinaemia and deposition of bile pigment in tissues. Clinically, jaundice is most readily identified in the sclera, mucous membranes and nonpigmented hairless skin. A rational approach to the investigation of jaundice relies on classification of the type of jaundice and then more specific diagnostic tests to establish a definitive diagnosis. Clearly more than one type may occur in the same patient at the same time and this is especially true in the case of intrahepatic and posthepatic jaundice.



Types of Jaundice



Prehepatic jaundice


Prehepatic jaundice typically occurs due to haemolytic anaemia. Under normal circumstances, the majority of plasma bilirubin is derived from the catabolism of haemoglobin released from ageing or damaged red blood cells that are phagocytosed by macrophages in the liver and spleen. Acute haemolysis, especially intravascular haemolysis, may result in hyperbilirubinaemia due to overwhelming of normal metabolic pathways.



Intrahepatic (hepatocellular) jaundice


Hepatocytes take up albumin-bound unconjugated (free, indirect) bilirubin from the circulation and then excrete conjugated (direct) bilirubin into the bile canaliculi. The bilirubin then travels via the bile duct into the gut lumen. Hepatic diseases may cause intrahepatic impairment of bile flow (cholestasis). Causes of intrahepatic jaundice typically involve inflammation of the hepatobiliary system, both acute and chronic. Examples are listed in Box 18.1.



BOX 18.1 Some causes of hepatic (hepatocellular) jaundice




Dogs



• Cholangiohepatitis

• Chronic active hepatitis

• Cirrhosis/fibrosis

• Leptospirosis

• Neoplasia (primary, secondary)

• Copper-associated hepatitis in Bedlington terriers (and other breeds)

• Drug-induced or toxic hepatitis (e.g. anticonvulsants; paracetamol (acetaminophen))


Cats



• Feline cholangitis/cholangiohepatitis complex

• Hepatic lipidosis

• Neoplasia, especially lymphoma

• Feline infectious peritonitis (FIP)

• Drug-induced or toxic hepatitis (e.g. diazepam and other anticonvulsants; paracetamol (acetaminophen))

• Cirrhosis/fibrosis


Posthepatic jaundice


Posthepatic jaundice typically occurs due to obstruction of the larger bile ducts. This obstruction may be intraluminal or due to extraluminal compression and a combination may occur in any one case. The most common causes of posthepatic jaundice are pancreatitis and pancreatic neoplasia causing bile duct compression. Other causes include inflammatory disorders of the biliary system, and obstruction of bile flow due to inspissated bile or cholelithiasis. Biliary tract rupture may also cause posthepatic jaundice.



Case example 1




Presenting Signs and Case History


A 5-year-old female neutered English springer spaniel presented with a 24-hour history of progressive lethargy, weakness and inappetence. Her owner had also noted her to be jaundiced. No other significant history was reported. The dog had a complete vaccination history but had not been vaccinated recently, and she was not receiving any drug therapy.

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Jaundice

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