Umbilical vein collateral circulation: the caput medusae in a newborn infant.

Extensive abdominal wall venous collaterals, with blood flow from the umbilicus toward the thorax, were observed in a newborn infant. Liver function studies and inferior vena cavagram were normal. The umbilical vein was isolated beneath the linea alba, but a probe could not be passed across the umbilical-portal vein junction in the liver. In the embryo, this is the point of "critical anastomosis" between the umbilical vein system of the enfolding abdominal wall and the omphalomesenteric (portal) vein system of the developing liver. Analysis suggests that the abdominal wall collateral veins represent persistence of the distal umbilical vein connections to the right side of the heart as a successful adaptation by the fetus to preserve umbilical venous return from the placenta. With assumption of extra-uterine circulation, and no further need for the umbilical vein collateral flow, the veins gradually recede, as occurred in the infant reported. Unlike the caput medusae of portal hypertension, the caput medusae of the newborn appears to be of no clinical consequence. Expectant observation of the collateral veins can be advised with high confidence for their gradual disappearance.