Common Bile Duct Size?

What is the normal size of the common bile duct?
I ask because my grandmother is having some health problems and her doctor mentioned something about her common bile duct and how the size was a little bigger than normal.
Doctors are not giving her a diagnostic yet.
Can you inform me about the Common Bile Duct and its proper size?

Various authors report different "normal" ranges for the diameter of the common bile duct. The consensus is that most people have a common bile duct diameter of around 5mm, +/- 1 mm. However, there are reports were people with no hepatobilliary disease have a "normal" common bile duct size up to 10 mm. Also, there is a correlation between common bile duct diameter and age. Most physicians would like to check things further if the common bile duct diameter is greater than about 7 mm, particularly if there are symptoms indicating hepatobilliary disease (abdominal pain with or without jaundice, fever etc.). Finally, even "normal" common bile duct sizes do not exclude the possibility of disease (such as stones).

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.