the choledochal cyst arises from dilatation of the common bile duct although other parts of the biliary tree, both intra- and extra-hepatic, may be involved. it is rare in the western world, most cases being described from japan. it may arise as a weakness in the duct wall.
the cystic structure appears in the right half of the liver. the fetal gall bladder may be separately identified. there is no polyhydramnios.
the cyst must be distinguished from duodenal atresia and other cystic structures in the liver, mesentery, omentum and ovary. duodenal atresia will usually be associated with polyhydramnios whilst intra-abdominal cysts will usually appear freely mobile within the abdominal cavity. a duplication cyst of the duodenum may have similar appearances to a choledochal cyst. a right multicystic dysplastic kidney or hydronephrosis will usually appear more posterior.
echo-free non-pulsatile area in right upper abdomen
cyst is located near the portal vein
dilated bile ducts may be seen
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