Fetal Liver, Ductus Venosus

FETAL LIVER AND DUCTUS VENOSUS

Conduit between portal veins and systemic veins. It is strategically situated as a shunt bypassing the liver, supplying oxygenated blood directly to the heart. Research suggests that 20-30% of umbilical blood flow enters the ductus venosus (the other 70-80% is directed towards the liver).
Blood flow through the ductus averages 40-60 mL min ^–1 kg^-1 at 20 weeks to less than 20 mL min^-1 kg^-1 at full term (1).
It has no branches.
The diameter of the inlet increases from a mean of 0.7mm to 1.5mm during the second half of the pregnancy (2)
High velocity channel that connects the left PV to the left hepatic vein or IVC.
It is an important regulator of fetal circulation, which is controlled by autonomic, neural and hormonal mechanisms (3).
It is not a passive vessel as a sphincter, which allows it to dilate or contract, controls its diameter.
The vessel is trumpet-shaped with a sphincter at its distal end that regulates flow by beta adrenergic distension or alpha adrenergic constriction. Prostaglandins are believed to maintain patency, in a fashion similar to the ductus arteriosus.

Kiserud T, Rasmussen S, Skulstad SM. Blood flow and degree of shunting through the ductus venosus in the human fetus. Am J Obstet Gynecol 2000;182:147-153.
Kiserud T, Rasmussen S, Skulstad SM. Blood flow and degree of shunting through the ductus venosus in the human fetus. Am J Obstet Gynecol 2000;182:147-153.
Kiserud T, Ozaki T, Nishina H et.al. Effect of NO, phenylepihrine and hypoxemia on the ductus venosus diameter in fetal sheep. Am J Physiol 2000;279:H1166-1171.
Rudolph AM. Distribution and regulation of blood flow in the fetal and neonatal lamb. Circ Res 1985;57:811-821.
Coceani F, Olley PM. The control of cardiovascular shunts in the fetal and perinatal period. Can J Pharmacol 1988;66:1129-1134.