In sonography of my father in law i have seen common bile duct is dilated and measures 1 cms. is it anything major about lever function? hiw to go abo

That is an: abnormal diameter for the common bile duct. It could indicate that the duct is obstructed, and potential reasons include stones, stricture, or mass. If your father has had a prior cholecystectomy, it may be post op chronic dilatation. Correlation with liver function tests along with additional imaging with CT and/or MRI and/or MRCP may be needed to determine why the duct is dilated.