Jaundice (Icterus)
Jaundice is classified as pre-hepatic (hemolytic), hepatic and post-hepatic (obstructive) depending on origin of the problem, and is characterized by yellowish discolouration of visible mucous membrane, and tissues. The obstructive jaundice may occur due to extra-hepatic biliary obstruction, or due to intra-hepatic primary cholestasis. It is more intense in obstructive and hepatocellular damage than when it is caused by excess destruction of red blood cells (RBC). The yellow pigment, bilirubin deposits in the plasma and other tissues. Bilirubin concentration in plasma increases (hyperbilirubinemia), if the production exceeds the excretory capacity of the liver. Jaundice may occur with or without impairment of bile flow. In impairment of bile flow, bilirubin metabolite is absent in the faeces and jaundice is very severe.
Etiology: Haemolytic jaundice is caused by bacterial toxins, babesiosis and inorganic and organic poisons. Bacillary haemoglobinuria and leptospirosis are characterized by intravascular haemolysis. Acute haemolytic anaemia is also seen in calves following drinking of large quantity of cold water, or drinking immediately after exercise in animals. Diffuse diseases of liver cause degeneration of hepatic cells due to toxic conditions that are enlisted under hepatitis. Obstructions of bile ducts by biliary calculi or obstruction of common bile duct by nematodes or infestation with trematodes are common in animals. The mechanical stasis of biliary flow is caused by fibrosed tissue.
Diagnosis: Failure of liver to dispose off bile pigments in the circulation may result in retention jaundice. This may be due to excessive destruction of red blood cells (RBCs). Haemolytic or damaged parenchymal cells are not able to excrete normal quantity of bile pigments (toxic jaundice). In toxic jaundice there is retention of bile pigments but anaemia is absent. If signs of anaemia accompany jaundice, haemolytic origin should be suspected.
Presence of urinary bilirubin and absence of urobilirubin from the urine and faeces indicate obstructive jaundice of extrahepatic type. When bile appears in the urine, one can be definite that either liver disease is present or bile duct is obstructed.
Treatment: The line of treatment suggested for the animals suffering from hepatitis is of value for its treatment.