Fetal extrahepatic vitelline vein aneurysm mimicking an umbilical vein varix

The differential diagnosis of fetal upper abdominal vascular dilatation is usually ascribed to an umbilical vein (UV) varix by most examiners. The possible prenatal differential diagnosis of an extrahepatic vitelline (portal) system origin has only been anecdotally reported.¹ To our knowledge, only 2 other cases of an intrahepatic portal vein system aneurysm (PVSA) have been reported in the prenatal period.^2,3 We present a rare case of a fetal extrahepatic PVSA, which substituted the UV as the blood carrier from the placenta. A PVSA is a rare abnormality, with reported incidence in adults of 0.43%.⁴ Serious complications such as intra-abdominal hemorrhage and thrombosis can follow.^4-6The particular sonographic features that differentiate it from a UV varix and its short postnatal outcome are described. A review of the prenatal literature, its assumed embryologic basis, and possible serious clinical postnatal sequelae are discussed.