Choledochal segmentation is the division of the choledochal duct into four segments: the upper duodenal segment, the posterior duodenal segment, the pancreatic segment, and the segment within the wall of the duodenum. 1. Upper duodenum: It refers to the location from the beginning of the common bile duct to the upper part of the duodenum in the human body, which is called the upper duodenum. 2. Posterior duodenum: This section of the bile duct is in the posterior part of the upper duodenum to the posterior part of the portal vein, which is called the posterior part of the duodenum. 3. Pancreatic segment: The bile duct is posterior to the head of the pancreas and is wrapped by a thin layer of pancreas in the groove of the common bile duct called the pancreatic segment, which is the channel for the excretion of bile as well as pancreatic juices. 4. Duodenal intramural segment: The bile duct passes obliquely through the medial side of the duodenum to join the pancreatic duct and is encircled by the sphincter muscle, and the opening part is in the duodenum, which is called the duodenal intramural segment. The common bile duct is an important part of the human body, the patient should pay attention to dietary regulation in life, to prevent excessive secretion of bile, causing common bile duct disease.