Key points
- Persistent right umbilical vein (PRUV) – the right umbilical vein fails to obliterate while the left umbilical vein usually regresses, the reverse of normal development.
- Seen in about 0.2% of fetuses (69 of 30,240 in the largest prenatal series).
- Intrahepatic PRUV drains into the right portal vein and is usually isolated and benign; extrahepatic PRUV bypasses the liver into the IVC or right atrium and carries a high rate of associated anomalies.
- May be supernumerary, with both umbilical veins patent.
Imaging findings
- US: on the transverse view of the fetal abdomen at the level of the stomach, the umbilical vein enters the liver on the right and the intrahepatic portal vein curves away from the stomach – the normal hook of the portal vein toward the stomach is reversed.
- The gallbladder lies medial to the umbilical vein instead of its normal lateral position.
- Doppler shows venous flow from the abdominal wall into the right portal vein and identifies the drainage site, separating intrahepatic from extrahepatic PRUV.
- The ligamentum teres deviates to the right; association with a left-sided gallbladder is described.
Classification
- Intrahepatic – joins the right portal vein, portal perfusion preserved, usually an isolated benign variant.
- Extrahepatic – bypasses the liver to drain into the IVC or right atrium, functioning as a portosystemic shunt, strongly associated with cardiac, renal, skeletal and chromosomal anomalies.
- Supernumerary – both the right and left umbilical veins persist.
Differential diagnosis
- Normal left umbilical vein – portal vein curves toward the stomach and the gallbladder is lateral to the vein.
- Extrahepatic PRUV – the vein bypasses the liver; Doppler shows drainage into the IVC or right atrium.
- Duplicated umbilical veins – two patent veins, one entering each portal branch.
What to do next
- Perform a detailed anomaly survey with fetal echocardiography; offer chromosomal microarray when PRUV is extrahepatic or additional anomalies are found.
- Isolated intrahepatic PRUV has a favorable prognosis – 68 of 69 fetuses were normal at birth in the largest series; reassure.
- Extrahepatic PRUV needs postnatal assessment of the portosystemic shunt and of the associated anomalies.
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