Ultrasound evaluation of common bile duct size.

A new sonographic technique for demonstration of the common bile duct is described in a prospective study of 200 patients. The mean diameter of the normal common duct was 4.1 mm. A common duct greater than 7 mm in diameter can be seen in (a) nonjaundiced patients with gallstones and/or pancreatitis, or (b) jaundiced patients with common duct obstruction by stone or tumor. A common duct greater than 11 mm in diameter is strongly suggestive of obstruction by stone or tumor.