The normal value of the internal diameter of the common bile duct may vary depending on the age and ethnicity of the person. Generally, the internal diameter of the common bile duct in young children is between 2-4mm; in children, it is between 4-6mm; in normal adults, it is between 6-8mm; and in the elderly, most of the internal diameter of the common bile duct will be between 9-12mm. If the internal diameter of the common bile duct in normal adults is greater than 10mm, it indicates a widening and requires further examination, as appropriate, to look for lesions such as stones, obstruction, and occupancy. If there is widening of the internal diameter of the common bile duct, there are often clinical manifestations, such as epigastric pain, fever and jaundice, and if these symptoms are accompanied by these symptoms, prompt medical attention should be sought and not ignored.