The ductus venosus is a bypass between the UMBILICAL VEIN and INFERIOR VENA CAVA in the fetal circulatory system. Closure usually starts immediately after birth when the blood pressure in the umbilical vein decreases. In patent ductus venosus, this closure fails to occur resulting in HEPATIC ENCEPHALOPATHY; HYPERAMMONEMIA, decreased liver function and mild fatty degeneration of the liver. It may be a hereditary autosomal recessive defect. OMIM: 601466
