I have a chronic bile duct disease which causes dilation, but I'm no doctor. Certainly you need followup to determine what is causing yours. But given that your recent liver blood tests are normal, immediate urgency isn't required. If you were suffering with a serious bile flow blockage, the damage would be reflected in the liver enzymes (back flow will destroy your hepatocytes affected within the pooling) and also elevated bilirubin levels (total and/or directed) would be present.
Hope this answers your question.
Is there a Dr online that can answer questions pertaining to bile duct dialation?