Liver and ductus venosus blood flows in fetal lambs in utero.

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Abstract
The circulation of the liver and ductus venosus was evaluated using the radionuclide-labeled microsphere technique in 24 chronically prepared fetal lambs. Catheters were placed in fetal descending aorta and inferior vena cava, and in a carotid artery and an umbilical vein; in 11 fetuses, a catheter was also inserted in a mesenteric vein that drained into the portal vein. After allowing 2-4 days for recovery from the stresses of anesthesia and operation, blood flow to the fetal liver and its various lobes and through the ductus venosus was measured. Total blood flow to the liver was 435 .+-. 122 ml/min per 100 g liver (mean .+-. SD), of which hepatic arterial flow represented 9%, portal venous flow 18% and umbilical venous flow 73%. Hepatic arterial and umbilical venous flows were approximately equally divided between left and right lobes, although portal blood flow was directed almost exclusively to the right lobe. The right lobe received 40% more total blood flow than the left, even though the left lobe weighed more than the right. Approximately 53% of umbilical venous blood flow but less than 9% of portal venous blood flow entered the ductus venosus; umbilical venous flow therefore accounted for more than 98% of ductus venosus blood flow. Ductus venosus flow showed a strong linear correlation with umbilical blood flow. There was no relationship between ductus venosus flow and gestational age. Apparently the liver receives a large blood flow primarily because of a large umbilical venous contribution. It is not clear whether the fetal liver requires this large flow and peculiar lobar distribution for normal function and growth, but is unlikely that the ductus venosus functions actively to maintain a stable blood flow to the fetal liver.

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