Absence of the ductus venosus with direct connection between the umbilical vein and right atrium.

Abnormalities of the ductus venosus are rare. We present the case of a dichorionic, diamniotic twin pregnancy in which complete absence of the ductus venosus, with direct communication between the umbilical vein and right atrium, was detected in one infant on antenatal ultrasonography. Autopsy confirmed the aberrant course of the umbilical vein, which also had an abnormal histological structure. Associated congenital anomalies included an ostium secundum type atrial septal defect, absent inferior vena cava, single left pulmonary vein, stenosed right pulmonary artery, proliferation of the hepatic arterioles with reduction of portal venules, and a duplex ureter. The literature is reviewed and pathogenesis relevant to this case is discussed.