Why do congenital shunts develop?
All mammalian fetuses have a large shunt (“ductus venosus”) that carries blood quickly through the fetal liver to the heart. Since the mother’s liver does the work of filtering out toxins, storing sugar, and producing protein for her unborn babies, liver function is not needed in the fetus. This ductus venosus is supposed to close down shortly before or after birth as the baby’s liver begins to work. In some individuals the shunt doesn’t close down; it is then called a “Patent Ductus Venosus”, or an intrahepatic shunt. In other animals, a blood vessel outside of the liver develops abnormally and remains open after the ductus venosus closes. This is called a congenital extrahepatic shunt. Why do animals with shunts have problems? In the normal animal, food and other ingested materials are broken down or digested in the intestines and absorbed into the portal blood stream, where they are carried to the liver. The liver stores some of the food for energy, processes some of it into safe ch
