The bile ducts are a network of tubes that transport bile, a digestive fluid made by the liver, from the liver and gallbladder to the duodenum. The system includes the intrahepatic bile ducts within the liver, the common hepatic duct, the cystic duct from the gallbladder, and the common bile duct, which is formed when the common hepatic and cystic ducts join together. Measuring the common bile duct is a standard part of right upper quadrant ultrasound, with a normal diameter generally considered to be less than 6 to 7 millimeters, though it may be slightly larger in older patients or those who have had their gallbladder removed. Dilation of the bile duct on ultrasound is an important finding that may indicate an obstruction from gallstones, tumors, or other causes.
Sonography Term