What is the upper limit of normal for the common bile duct on ultrasound: How much do you want it to be?

Conventionally, the upper limit of normal for the common bile duct as measu red by ultrasound is considered to be 6 mm. This review is a somewhat perso nalized account of how that number became the convention and cautions the r eader to avoid being slavish in the use of this number. Two specific cautio ns are not to apply this limit to older patients and to consider where in t he common bile duct the measurement was taken, as measurements taken closer to the pancreas may be larger than ones closer to the liver. (C) 2000 by A m. Cell. of Gastroenterology.