Abnormalities of the fetal central veins and umbilico-portal system: Prenatal ultrasonographic diagnosis and proposed classification

Objectives: Anomalies of the fetal venous system are poorly documented and their pathogenesis is not well understood. The present study was undertaken to review the spectrum of fetal central veins and umbilico-portal system anomalies, and to propose a classification system. Methods: A 7-year restrospective survey was conducted. Results: Nineteen fetuses showed abnormal connection between central veins and the fetal heart. Three fetuses showed abnormal connections of the cardinal veins, two of which had interruption of the inferior vena cava, and one had isolated persistent left superior vena cava. Anomalies of pulmonary veins were seen in four fetuses: in two with asplenia syndrome, a vertical confluent pulmonary artery was observed. In a further two cases total anomalous pulmonary venous connections were found. Abnormalities of the umbilical vein (UV) were seen in 10 cases; seven had persistent right UV, and three had a spectrum of anomalies: One had abnormal connections of the UV to the left iliac vein associated with agenesis of the ductus venosus (DV) and hydrops fetalis. One case showed in utero occlusion of the D V by echogenic foci that resulted in a persistent left proximal UV and porto-systemic shunt. One case had obliteration of the D V secondary to in utero fetal hepatic fibrosis. Abnormalities of the vitelline veins or portal system were demonstrated in two cases. One had a left portosystemic shunt which resolved spontaneously at 3 months of age, and one had secondary partial occlusion of the left portal system with liver echogenicities and direct communication of the UV with the right atrium. None of the 19 cases had an abnormal karyotype or evidence of in utero infection. Conclusions: Detection of various fetal vein anomalies in utero is feasible. The anomalies vary according to embryologic precursors or etiology. Two major mechanisms seem to be involved in the genesis of fetal vein anomalies: in most cases primary maldevelopment of the venous system occurs, while in the minority secondary anomalies from possible thromboembolic events or systemic disease may play a role.