Follow-up sonographic studies of three infants, whose initial sonograms showed findings suggestive of choledochal cyst, demonstrated disappearance of cystic dilatation of the common bile ducts. The phenomena could be accounted for by acute common bile duct obstruction secondary to bile sludge. Bile plug syndrome should also be included in the differencial diagnosis. When a cystic or fusiform dilatation of the common bile duct is seen on sonogram, conservative management must be the choice of approach unless the finding is proven to unchanged over a period of time and irreversible.