Absent ductus venosus in the fetus: review of the literature and first report of direct umbilical venous drainage to the coronary sinus

The ductus venosus connects the portal and umbilical veins with the inferior vena cava and acts as a sphincter to protect the fetus from placental overcirculation. Its absence usually causes hydrops fetalis and is associated with high mortality rate, chromosomal anomalies and congenital malformations. In this condition, the umbilical vein almost always drains directly into right-sided structures such as inferior vena cava or right atrium. We reviewed the literature and describe the first case of a fetus with absent ductus venosus and direct connection of the umbilical vein to the coronary sinus.