Accuracy of common hapatic duct size in the evaluation of extrahepatic biliary obstruction.

High-resolution real-time ultrasound sector scanning is helpful in showing the normal common hepatic duct. The authors evaluated the accuracy of using a 4-mm internal diameter as the upper limit of normal in evaluation of obstruction. Of 98 patients with jaundice or right-upper-quadrant pain whose duct exceeded 4 mm, obstruction was proved in 84. Fourteen patients had no radiographic or pathological evidence of obstruction, but 7 had undergone cholecystectomy and clinical evidence suggested another 6 had passed a stone before or after the ultrasound study. Of 72 patients with a duct greater than or equal to 4 mm, only one had obstruction; a mass blocked the right and left hepatic ducts. The sensitivity of the test is 99%, the specificity 87%. Thus if the common hepatic duct is more than 4 mm in internal diameter on ultrasound, extrahepatic biliary obstruction is probably present.