The width of normal human extrahepatic common bile duct is usually within 8mm, and the dilatation of extrahepatic common bile duct of 9mm is a mild dilatation that should cause alarm. The width of the extrahepatic bile duct is 9mm, which is a mild dilatation of the bile duct. The normal width of the common bile duct is within the range of 6-8mm, but it is abnormal if it is more than 10mm. The width of the extrahepatic bile duct of 9mm may be caused by individual differences or the early stage of dilatation of the bile duct, but it should also be alerted to a certain extent. When the width of the extrahepatic bile duct reaches 9mm it may be suggestive of early stones or inflammation, conditions that lead to poor drainage of bile and increased pressure in the dilated common bile duct. It is recommended that mild extrahepatic bile duct dilatation of 9mm accompanied by abdominal pain and dyspepsia should be promptly treated by a doctor or followed up for observation.