Fetal development of the retrohepatic inferior vena cava and accessory hepatic veins: Re-evaluation of the Alexander Barry's hypothesis.

The retrohepatic inferior vena cava (IVC) is commonly considered to originate from the right vitelline or omphalomesenteric vein. In contrast, Alexander Barry hypothesized that one of the hepatic veins grows to merge with the subcardinal vein and develops into the retrohepatic IVC. We re-examined fetal development of the retrohepatic IVC and other related veins using serial histological sections of 20 human fetuses between 6 and 16 weeks of gestation. At 6-7 weeks, when a basic configuration of the portal-hepatic vein systems had just been established, one of hepatic veins (i.e., the posterocaudal vein in the present study) had grown caudally to reach the posterocaudal surface of the liver, and notably, extended into the primitive right adrenal gland (five of the eight early-staged fetuses). Because the inferior right hepatic vein (IRHV) and retrohepatic IVC appeared at the same developmental stage, it is likely that any peripheral remnants of the posterocaudal vein would continue to function as primary drainage territory for the IRHV. The caudate vein developed rapidly in accordance with marked caudal and leftward extension of Spiegel's lobe at 12-16 weeks. Thin accessory hepatic veins developed later than the caudate vein and IRHV. The present results supported Barry's hypothesis.