The hepatic ducts are the bile drainage channels that collect bile produced by liver cells and transport it toward the gallbladder and intestine. The right and left hepatic ducts emerge from their respective liver lobes and join to form the common hepatic duct, which then merges with the cystic duct from the gallbladder to form the common bile duct. On ultrasound, the intrahepatic bile ducts are normally not visible or appear as tiny tubes running alongside the portal vein branches. When they become dilated due to downstream obstruction, they become visible as tubes running parallel to the portal veins, creating a double-barrel or parallel-channel sign that is an important indicator of biliary obstruction.
Sonography Term