Jaundice

1. Introduction Jaundice is a yellow discoloration of the skin or sclera of the eye(see the pic.on the right) this is due to the presence of bilirubin in the plasma and is not usually detectable until the concentration is greater than about 50 µmol/L Normally the bilirubin concentration in plasma is less than 22 µmol/L Bilirubin is derived from the tetrapyrrole prosthetic group found in hemoglobin and the cytochromes. It is normally conjugated with glucuronic acid to make it more soluble and excreted in the bile. there are three main reasons why bilirubin may rise in the blood * Hemolysis , the increased hemoglobin breakdown produces bilirubin, which overloads the conjugating mechanism. * Failure of conjugating mechanism within the hepatocyte. * Obstruction in the biliary sytem. Jaundice Biochemical tests Bilirubin metabolites are responsible for the brown coloration of feces. If bilirubin dose not reach the gut, stools become pale in color. Bilirubin in the gut is metabolized my bacteria to produce stercobilinogen . This is partly reabsorbed and re-excreted in the urine as urobilinogen, and maybe detected by simple biochemical testes. when high levels of conjugated bilirubin are being excreted , urine maybe a deep orange color . This combination of pale stools and dark urine is characteristic of exrahepatic obstruction of the biliary tract . This is often amenable to surgery , hence the term surgical jaundice. Differential diagnosis Jaundice maybe a consequence of hemolysis, cholestasis or hepatocellular damage. In addition there are inherited disorders of bilirubin metabolism. Gilbert’s disease is the most common and causes a mild unconjugated hyperbilirubinaemia because of defective hepatic uptake of bilirubin .in this condition bilirubin levels rise on fasting . Conclusions * Jaundice indicates that there is an elevated concentration of bilirubin in serum. * In neonates it is important to determine the concentration of unconjugated bilirubin in order to decide what treatment is required. * In adults, the most common cause of jaundice is obstruction and this is confirmed by the elevation of both bilirubin and alkaline phosphatase . Hemolysis cause increased bilirubin production that lead to predominantly unconjugated hyperbilirubinaemia this is combination with immature liver function, is commonly occurred in babies. Extrahepatic biliary obstruction gallstones can partially or fully block the bile duct, both bilirubin & alkaline phosphatase are raised. Hepatocellular damage obstruction may be secondary to damage to hepatocytes by infection or toxins, rather than damage to the biliary tract. The most common causes of acute jaundice seen in adults are viral hepatits and paracetamol poisoning. In these cases not only are bilirubin and alkaline phosphatase levels raised but AST and ALT are elevated indicating hepatocellular damage. School of medicine , Sulaymania university Created by: Ali Kareem, Abdulameer Mukhtar, Roza Azad, Fnn Fareed. E-mail: Tallo_94@ymail.comTelephone: 0771 775 237 0