If the cystic duct is obstructed, usually by a stone which has failed to pass through to the CBD, the normal flow of bile from the gallbladder is interrupted. Chronic cystic duct obstruction causes the bile to be replaced by mucus secreted by the lining of the gallbladder, resulting in a mucocoele. The biliary ducts remain normal in calibre. If the gallbladder looks dilated, make a careful search for an obstructing lesion at the neck; a stone in the cystic duct is more difficult to identify on ultrasound as it is not surrounded by echo-free bile (Fig. below )
Stone impacted in the neck of the gallbladder. The lefthand image is a TS through the neck demonstrating the impacted stone. The right-hand image demonstrates the dilated gallbladder containing fine echoes from inspissated bile.
LiveJournal Tags: Ultrasound images Mucocoele of the gallbladder