Jaundice
It is a clinical condition characterised by yellowish discolouration of skin, sclera, conjunctiva and mucous membrane due to deposition of bile pigments. It is due to increased amount of bile pigment in the body. Bile pigments are produced as degradation products of haemoglobin. These are then released into circulation by the RE cells. These pigments circulate in combination with albumin as these pigments called haemobilirubin are not water soluble. Increased concentration of haemobilirubin in blood may occur due to its excess formation as a result of excess RBC destruction (haemolysis). The jaundice caused due to above reason is called haemolytic jaundice (Acholuric = absence of bile pigment in urine). The typical example is haemolytic disease of the newborn . It also occurs in malaria, etc. This type of jaundice may also occur due to accumulation of haemobilirubin owing to inability of the liver to clear them (see physiological jaundice).
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| photo create by- BLACKDAY |
In the normal way the haemobilirubin is taken up by the hepatocytes and then conjugated and excreted in bile. Therefore, in compromised liver function, jaundice may occur as stated above, i.e., due to accumulation of haemobilirubin in the body.
The conjugated bilirubin, excreted in the bile, passes through the biliary tract to the intestine. Now, obstruction anywhere in the tract due to any reason (mechanical or non- mechanical) will lead to backflow of the conjugated bilirubin to the blood and will result in obstructive jaundice. Here the conjugated bilirubin from the hepatocytes cannot enter into the bile canaliculi, so move into the sinusoidal blood.
Therefore, jaundice may be due to conjugated bilirubin (obstructive) or due to haemobilirubin (haemolytic) but mixed picture is frequently obtained particularly in jaundice due to hepatocellular disease. In this latter condition, disease of the liver cells causes accumulation of haemobilirubin as well as backflow of conjugated bilirubin to the blood. Accumulation occurs as the diseased hepatocytes can not clear the normal bilirubin load and backflow occurs due to obstruction of small intrahepatic bile channels as a result of swelling (oedema) of the diseased liver cells.
Jaundice is also classified as prehepatic, hepatic and post hepatic according to the site of origin of the disease in relation to the liver. Prehepatic jaundice is due to reasons before the liver as in haemolysis (equivalent to haemolytic type). The causes of hepatic jaundice are within the liver as in viral hepatitis and the jaundice is of mixed type. Post hepatic Jaundice is produced due to obstruction in the biliary tree i.e., aiter the liver and is equivalent to the obstructive ype as stated above.
Physiological jaundice: In the newborn, haemolysis is normally rapid, so there is more bilirubin production. Together with this there may be deficiency of the enzyme glucuronyl transferase in the first few days of life. All these lead to a transient jaundice which is usually cured automatically. This type is called physiological jaundice. Sometimes it needs to be treated by photo therapy with white light when bilirubin is converted to lumirubin and disposed quickly.
Diagnosis:
Various types of jaundice can be diagnosed by identifying the type of bilirubin involved. This is done by Van den Bergh reaction (see below). The features of jaundice also depend on the type of bilirubin (Table). In haemolytic jaundice urine is not yellow as haemobilirubin-albumin complex cannot pass through the filter in kidney due to their larger size. But stool becomes high coloured as excretion of conjugated bilirubin increases through the bile to the intestinhe. Urobilinogen content in urine also increases.
In case of obstructive jaundice the conjugated bilirubin passes easily through urine and the urine becomes yellow coloured, but stool becomes clay coloured as bile does not enter into the intestine which may also lead to steatorrhoea. (Cholestatic jaundice is obstructive jaundice due to any reason but without any disease of the hepatocytes; here urobilinogen excretion through urine decreases). In the mixed type of jaundice, features of both of the above types are found.