Jaundice is a symptom and sign of yellowing of the skin, mucous membranes and sclera due to elevated bilirubin in the blood serum. Bilirubin in the blood is normally in dynamic balance, with normal values of total bilirubin ranging from 1.7 to 17.1 ummol/L. This includes direct bilirubin (normal values 0 to 3.42 ummol/L) and indirect bilirubin (1.7 to 13.68 ummol/L). There are various causes of jaundice. The destruction of red blood cells in the blood produces a large amount of hemoglobin, which eventually forms indirect bilirubin, which combines with glucuronic acid in the liver to form direct bilirubin, which then passes through the bile duct into the small intestine, where it is reabsorbed and enters the liver. Therefore, abnormalities in any part of this pathway can cause jaundice. The common clinical causes are as follows: 1, hemolytic jaundice: due to the destruction of a large number of red blood cells, a large amount of indirect bilirubin is produced, exceeding the metabolic capacity of the liver, resulting in jaundice. It is characterized by elevated indirect bilirubin. This condition is mostly caused by internal diseases, especially the possibility of hematologic diseases. 2. Hepatocellular jaundice: Jaundice caused by severe damage to liver cells. It is characterized by elevated direct and indirect bilirubin. The etiology is mainly internal diseases, viral hepatitis, cirrhosis, toxic hepatitis, sepsis and other diseases that may damage the liver can cause this condition. 3, obstructive jaundice: Blockage of either the small intrahepatic bile duct or the extrahepatic common hepatic duct or common bile duct can cause varying degrees of bile passage obstruction, causing bilirubin in the bile to flow back into the blood, resulting in jaundice. Characteristically, direct bilirubin is predominantly elevated. It may be accompanied by symptoms such as itching of the skin, darkening of the urine and lightening of the stool color. Stones, inflammation and tumors of the biliary tract are common causes and mostly require surgical management.