Jaundice Study Resources

JAUNDICE Causes of jaundice: These can be divided into two major categories: Disorders causing predominantly unconjugated hyperbilirubinaemia: Over-production of bilirubin (pre-hepatic jaundice) Jaundice occurs when there is increased destruction of red blood cells (haemolysis). The liver cannot process all the excess bilirubin produced, which leads to a build up of unconjugated bilirubin in the bloodstream. Haemolysis is caused by a range of diseases including malaria, some drug reactions, and genetic diseases such as sickle cell anaemia. Impaired uptake or conjugation of bilirubin by the liver Certain medications, such as rifampicin, can interfere with the uptake of bilirubin by the liver and thus cause jaundice. Abnormalities in the conjugation can also cause jaundice. Gilbert’s syndrome, which is caused by deficiency of glucuronyl transferase, is a common cause of defective conjugation of bilirubin. Disorders causing mixed unconjugated and conjugated hyperbilirubinaemia: Impaired bilirubin secretion into bile canaliculli Jaundice can occur when there is defective secretion of bilirubin from the liver into the bile canaliculli. This can be caused by impaired secretion of bilirubin by hepatocytes (e.g. rare familial Dubin-Johnson syndrome) or by destruction of the intra-hepatic bile ducts by diseases such as primary biliary cirrhosis. Liver disease Damage to the hepatocytes can cause impairment of the bilirubin uptake, conjugation and excretion. Although liver damage produces mixed hyperbilirubinaemia, an increase in the conjugated bilirubin usually predominates, as excretion is the rate- determining step. The most common causes of jaundice due to liver disease are viral and alcoholic hepatitis. Obstruction of the bile ducts (post-hepatic jaundice) The most common causes of jaundice due to obstruction of the bile ducts are gall stones in common bile duct (choledocolithiasis) and cancer of the head of the pancreas. This type of jaundice leads to an increase of predominantly conjugated bilirubin Physiological Jaundice This is the jaundice seen in 50-60% of new born babies in their first week of life. It is due to the breakdown of adult haemoglobin, leading to a rise in [unconjugated bilirubin] which is not processed due to the low expression of glucurosyltransferase in newborns. Furthermore the child’s gastrointestinal tract lacks intestinal flora to convert bilirubin to urobilinogen and stercobilin. Breast Feeding Induced Jaundice • • • • A new borns gastrointestinal tract lacks intestinal flora to convert bilirubin to urobilinogen and stercobilin. Thus bilirubin will be deconjugated at the brush border by B-glucuronidases and reabsorbed. The enterohepatic circulation is also stimulated (resulting in increased reabsorption. 3-a-200prenandiol from breast milk also inhibits UDPGA Lipoprotein lipase in breast milk result in free fatty acids which also inhibit glucuronyl transferase Symptoms associated with jaundice: • Dark urine – Increased excretion of conjugated bilirubin causes dark urine. Unconjugated bilirubin is not water soluble and therefore is not excreted by the kidneys • Pale or clay-coloured stools – Metabolites of bilirubin excreted by the liver into the intestines give faeces their normal brown colour. When bile duct obstruction occurs, the stools may appear pale or clay-coloured due to lack of pigmentation. • Pruritus – The cause of pruritis (itchy skin) in the setting of jaundice is not known but is thought to be due to a build up in the skin of bile salts or other substances usually excreted by the biliary system.