2.6.1\ Scanning Methods

The patient should be on fast for 8–12 h with a supine position. The subcostal and right upper abdomen longitudinal scanning are performed. After scanning the longitudinal section of the porta hepatis, the transducer rotates 30° clockwise to parallel to the middle line approximately.

2.6.2\ Section Structure

Major areas: the common bile duct divides the common bile duct into the proximal, middle, and distal segments. Extrahepatic portions include the common hepatic duct, common bile duct, and a small portion of the distal right and left hepatic duct. At the porta hepatis, the proximal common bile duct runs anterior to the right and main portal vein and the right hepatic artery. The mid-duct runs posterior to the duodenum. Inferiorly the distal common duct enters the head of the pancreas and travels along the posterior-most aspect of the pancreatic head. Ancillary areas: the right portal vein, the pancreatic head, the right liver lobe, and the oblique section of the inferior vena cava. The common biliary duct runs down through the pancreatic head in about 2/3 and runs down in a groove on the posterior surface of the pancreatic head in about 1/3.

2.6.3\ Measuring Methods

and Normal

The inner diameter and length of the common bile duct, the common hepatic duct, and the right hepatic duct are measured. The common bile

duct varies in caliber along its course. The proximal diameter measurement should be made in the widest, generally on a level with the porta hepatis, mid segment measurement should be on a level with the upper edge of the pancreas and the distal segment measurement on a level with the posterior-inferior of the pancreatic head.

Normal: The normal value of inner diameter should be <0.6 cm, 0.6–0.8 cm as the critical value; be sure to follow up observations or conduct further examination. When inner diameter is larger than 0.8 cm, common bile duct dilatation can be affirmed. Bile duct diameter may be wider in patient who accepted cholecystectomy. The inner diameter will increase with time over, but rarely more than 1.0 cm.

2.6.4\ Clinical Application Value

This section is the standard section of the common hepatic duct and the common bile duct and can be used to measure the diameter and diagnosis of the obstruction; the presence of expanded, narrow, calculus, or space-occupying lesions; as well as lesions near the porta hepatis area.

The length of the common bile duct shown can indicate the level of the obstruction. The abnormalities may come from the common bile duct, pancreas or around pancreas, and ampulla of Vater.