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

Abstract

SUMMARY We evaluated the circulation of the liver and ductus venosus, using the radionuclide-labeled mkrosphere technique, in 24 chronically prepared fetal lambs. We placed catheters in fetal descending aorta and inferior vena cava, and hi a carotid artery and an umbilical vein; in 11 fetuses, we aho Inserted a catheter hi a mesenteric vein that drained into the portal vein. After allowing 2-4 days for recovery from the stresses of anesthesia and operation, we measured blood flow to the fetal liver and hs various lobes and through the ductus venosus. Total Mood 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. However, there was no relationship between ductus venosus flow and gestational age. The results suggest that the liver receives a large Mood flow primarily because of a large umbilical venous contribution. It is not dear whether the fetal liver requires this large flow and peculiar lobar distribution for normal function and growth. It is unlikely, however, that the ductus venosus functions actively to maintain a stable blood flow to the fetal liver. THE LIVER of the fetus receives its blood supply from the hepatic artery, portal vein, and umbilical vein. Total blood flow to the fetal liver must be high, because a large umbilical venous blood flow passes through the liver. Nevertheless, the actual flow that reaches the liver from all three vascular sources has not been measured previously. The relative contributions of hepatic arterial and portal and umbilical venous blood flows to the various lobes of the liver also have not been studied quantitatively. Anatomically, the left lobe of the liver is supplied by branches of the umbilical vein, while the right lobe is supplied by portal venous branches 11 (Fig. 1). Except for occasional small branches, no umbilical blood vessels extend into the right lobe, and no portal blood vessels reach the left lobe. Branches of the hepatic artery supply both lobes, but arterial flow to the whole liver is small.