Jaundice is a common symptom and sign that occurs when serum bilirubin is higher than normal due to impaired bilirubin metabolism, resulting in elevated concentrations of bilirubin in the sclera, skin, mucous membranes, body fluids, and other tissues. Clinically, the sclera, mucous membranes, skin and other tissues are stained yellow. It is not an independent disease, but a symptom and sign of many diseases, mostly seen in certain diseases of the liver, biliary system, pancreas and hematological system. Because the sclera contains more elastin and has a stronger affinity for bilirubin, scleral yellowing is often detected before mucous membranes and skin in patients with jaundice. When the total serum bilirubin is 17.1 to 34.2 μmol/L, and jaundice is not visible to the naked eye, it is called occult jaundice; when the blood-stained total bilirubin concentration exceeds 34.2 μmol/L, jaundice can be detected clinically, also called dominant jaundice. Classification of jaundice Hemolytic jaundice (prehepatic jaundice): due to a large number of destruction of red blood cells for various reasons, resulting in a significant increase in unconjugated bilirubin, exceeding the conversion capacity of the liver, but the conjugated bilirubin is normal. Hemolytic anemia: genetic spherocytosis, streptocytic anemia, etc. Presence of hemolytic factors in the plasma: physical: erythrocyte damage caused by artificial valves, chemical: application of drugs such as quinine, exposure to arsenical hydrogen, etc., biological: venomous bacteria and snake venom; immune: repeated multiple transfusions, blood type-mismatched transfusions, autoimmune hemolysis, etc. Other. Positive yellow skin: yellow vivid as orange. Hepatocellular jaundice (hepatogenic jaundice): due to hepatocellular lesions, the liver function is reduced, so that the uptake, conversion and excretion of bilirubin by the liver is impaired. On the one hand, the liver cannot convert unconjugated bilirubin into conjugated bilirubin, which increases unconjugated bilirubin in the blood; on the other hand, the lesion area compresses the capillary bile ducts, which causes conjugated bilirubin to flow back into the blood, and conjugated bilirubin in the blood also increases. (CB>30%) Common causes: viral hepatitis, toxic hepatitis, advanced cirrhosis, etc. golden yellow skin; obstructive jaundice (post-hepatic jaundice); bile cannot be drained and stagnates in the bile ducts due to biliary obstruction, causing increasing pressure in the upper bile ducts and eventually dilating the small bile ducts and capillary bile ducts, increasing permeability or even rupture, causing bile to return to the blood and increasing blood-conjugated bilirubin; intrahepatic cholestasis (cholestatic, pharmacologic, idiopathic, etc.); mechanical obstruction of the intrahepatic bile ducts ( primary biliary cirrhosis, intrahepatic bile duct stones, biliary sclerosis, etc.); mechanical obstruction of extrahepatic bile ducts (stones, tumors, bile duct strictures, parasites, etc…) ( bile duct compression factors: periampullary cancer, pancreatic head cancer, gastric cancer lymph node metastasis, etc.); Yin yellow: yellow obscure like smoke.