What is the maximum diameter of the common bile duct in mm?

The maximum diameter of the common bile duct is generally accepted to be around 8 mm in adults. This measurement provides a useful reference for clinicians when evaluating for pathological conditions such as choledocholithiasis (bile duct stones) or strictures, which can lead to bile duct dilation. In clinical practice, a common bile duct measuring larger than 8 mm is often investigated further due to the potential for underlying issues.

Understanding this measurement is fundamental in abdominal ultrasound interpretation, as normal variations, age, and certain physiological states can affect the duct's size. However, 8 mm is widely recognized as the upper limit of normal in most adults, making it the correct answer in this context.