Serum conjugated bilirubin is the direct bilirubin among liver functions. The normal values of serum bilirubin for patients are between 3.4-17.1 μmol/L for total bilirubin, 0-6.8 μmol/L for direct bilirubin, and 1.7-10.2 μmol/L for indirect bilirubin, all within this range are called normal values. If a patient has an elevated total bilirubin, the total bilirubin is between 17.1-34.2 μmol/L. In this case, the patient is usually considered to have occult jaundice, which means that although the patient has elevated bilirubin, the patient’s skin and sclera are generally not detected by the naked eye. If the patient’s bilirubin is further elevated and the total bilirubin is above 34.2 μmol/L, the patient is considered to have yellow staining of the skin and sclera that can be detected by the naked eye. If direct bilirubin is predominantly elevated, that is, serum conjugated bilirubin is predominantly elevated, and there is a combination of alkaline phosphatase and GGT elevation. The most common cause of obstruction is a stone in the common bile duct. In such cases, the patient needs to undergo further ultrasound of the upper abdomen and MRCP to confirm the diagnosis and then perform a stone extraction procedure for common bile duct stones.