In vivo measurements of the internal and external diameters of the common bile duct in man.

As in other studies, it was not possible to define precisely the normal size of the common bile duct measured either externally or roentgenographically. However, the roentgenographically measured diameter of the common bile duct appears superior to the external width of the common bile duct in discriminating between patients with, and without, common bile duct disease. If the common bile duct was 1 centimeter or less roentgenographically, then only one of 78 patients studied had common bile duct disease, while all patients with common bile ducts 1.5 centimeters or larger had common bile duct disease. The range from 1.1 to 1.4 centimeters was indeterminate as a predictor of disease, since two of 19 patients in this group had common bile duct calculi. The utilization of the internal diameter instead of the external diameter of the common bile duct as a predictor of disease could be especially important in the clinical separation of patients with medical from surgical jaundice when noninvasive diagnostic tests, such as ultrasound and computerized tomography, are used.