From the Guidelines
The common bile duct is a vital structure approximately 7-11 cm in length and 5-10 mm in diameter that plays a crucial role in bile transport from the liver to the duodenum. The structure of the common bile duct is complex, forming when the common hepatic duct joins with the cystic duct from the gallbladder 1. Anatomically, the common bile duct descends in the hepatoduodenal ligament, passing posterior to the first part of the duodenum before traversing through the head of the pancreas. It terminates at the ampulla of Vater on the medial wall of the second part of the duodenum, where it typically joins with the main pancreatic duct to form a dilated chamber called the hepatopancreatic ampulla. The distal end contains the sphincter of Oddi, a muscular valve that regulates bile flow into the duodenum.
Key Characteristics of the Common Bile Duct
- Length: approximately 7-11 cm
- Diameter: 5-10 mm
- Forms from the junction of the common hepatic duct and the cystic duct
- Descends in the hepatoduodenal ligament
- Passes posterior to the first part of the duodenum and through the head of the pancreas
- Terminates at the ampulla of Vater
- Joins with the main pancreatic duct to form the hepatopancreatic ampulla
- Contains the sphincter of Oddi for regulating bile flow
Histologically, the common bile duct has a mucosa lined with simple columnar epithelium, a lamina propria containing scattered glands, a muscularis layer (more prominent distally), and an outer fibrous adventitia 1. This structure allows for the controlled delivery of bile to aid in digestion, particularly of fats, while preventing reflux of duodenal contents back into the biliary system. Understanding the structure and function of the common bile duct is essential for managing conditions like choledocholithiasis, where bile duct stones can cause obstruction and potentially life-threatening complications 1.
From the Research
Structure of the Common Bile Duct
The common bile duct is formed by the junction of the cystic and common hepatic ducts.
- The cysticohepatic junction was adequately visualized in 70% of cases, with medial junctions noted in 18% and a spiral configuration in 32% 2.
- The point at which the cystic duct connects to the extra-hepatic bile duct delineates the division between the common hepatic duct and the common bile duct 3.
- The cystic duct enters the hepatic duct in the distal third of the extrahepatic biliary tree in 10% of patients 2.
- Understanding the anatomy of the cystic duct and its junction with the common hepatic duct is essential for endoscopic management of biliary tract disease and for preventing iatrogenic injury during surgical, endoscopic, and percutaneous procedures 2, 3.
Variations in Cystic Duct Anatomy
- An 11% occurrence of parallel duct systems was noted, which is less frequent than expected 2.
- The two orifices of the cystic duct, one connecting to the gallbladder and the other to the extra-hepatic bile duct, have not been fully described in literature, but their naming is highly relevant for interventions relating to the gallbladder and the biliary tree 3.