Right ligamentum teres joining to the right branch of the portal vein.

Ligamentum teres joining to the right branch of the portal vein in a 79-year-old Japanese male cadaver was noted during student dissection at Kumamoto University in 2004. The ligamentum teres entered the liver along the left side of the gallbladder fossa. The quadrate lobe was not distinguished from the left lobe in the visceral surface. When the liver parenchyma was removed by tearing off to expose the branches of the portal and hepatic veins, it was clarified that the ligamentum teres unusually joined to the bifurcation of the upper anterior and lower anterior branches of the right branch of the portal vein. The ligamentum teres is the remnant of the umbilical vein working throughout fetal life. Initially a pair of the umbilical veins entered the sinus venosus. During the fourth and fifth weeks they connect to the hepatic sinusoids, which become the portal and hepatic veins, and the parts entering the sinus venosus of both umbilical veins disappear. By the eighth week, as all remainder of the right umbilical vein disappears, the left umbilical vein is the only one to carry blood from the placenta to the liver. It results in the ligamentum teres joining to the left branch of the portal vein. However, in the present case it is thought that the right umbilical vein remained instead of the left one for some reason, and it then became the right ligamentum teres joining to the right branch of the portal vein.