Classification of Umbilical Vein Anomalies Based upon Cases in Dead Fetuses

Yu, Hee Chul; Cho, Baik Hwan; Hwang, Yong

Abstract

BACKGROUND: Prior reports of umbilical vein variation were strongly associated with several congenital anomalies. This suggests that the incidence of umbilical vein anomaly was more frequently seen in dead fetuses than in liveborn infants because the leading causes of stillbirth are chromosomal and/or congenital anomalies. The developing liver exerts a profound influence in modifying the primitive vitelline and umbilical veins. This study was undertaken to identify the umbilical vein variations and the associated hepatic and perihepatic structural anomalies in dead fetuses.
METHODS
Dissection was done in eighteen dead fetuses who had undergone delivery at Chonbuk National University Hospital between December 1996 and February 1998. The weight ratios of the liver to the body and the right to the left hepatic lobes and the distal attachment of umbilical vein, including the presence of hepatic fissures and ligaments, were examined. According to the gestational age, the cases were divided into two groups (group 1: < 32 weeks, 13 cases; group 2: > or = 32 weeks, 5 cases).
RESULTS
The gestational age of the fetuses ranged from 19 to 39 weeks. The fetal liver constituted 3.7% and 4.0% of the total fetal body weight for group 1 and 2, respectively. The mean weight ratio of the right to the left hepatic lobe was between 1:1.4 and 1:1.5. There were no gross morphologic abnormalities in 9 cases. Eighteen kinds of chromosomal and congenital anomalies, including omphalocele, anomalous hepatic segmentation, hypogenesis of the hand and the foot, syndactyly, polycystic kidney, etc., were observed in 9 dead fetuses. A case of an abnormal distal attachment of the umbilical vein was identified. The umbilical vein drained into the dilated extrahepatic portal vein directly. The hepatic segments and fissures were completely normal, but ligamentum teres was not identified in this case. A peculiar hepatic segmental anomaly due to whole organ herniation through a defect in an omphalocele was observed.
CONCLUSIONS
The weight of the liver of the dead fetuses was relatively small in both groups. No weight shift of left to right was recognized. The incidence of congenital anomalies was much higherin the dead fetuses (50%) than in the live births (0.7-1.98%). There were two hepatic anomalies (11.1%), including segmentation and distal attachment of the umbilical vein. The authors reviewed all reports of umbilical vein anomalies and propose a classification for umbilical vein variations focused on the distal points of attachment. All variations of the umbilical vein tend to fall into two main groups. In the first group, the veins have distal points of attachment into portal vein systems. In the second group, the veins have distal points of attachment into systemic veins.