Structure, calcifications, and early atherosclerotic lesions
With a single umbilical artery a unique haemodynamic situation arises during fetal development, resulting in a different calibre and structure of the iliac arteries on the two sides of the body. On the side of the single umbilical artery, the enlarged iliac arteries have the structure of elastic arteries, whereas the smaller and thin-walled iliac arteries, which do not participate in the placental circuit, show the typical structure of muscular arteries. These differences of the arterial structure determine the morphological pattern of early calcifications which are regularly present in the iliac arteries on both sides of the body, but are usually more conspicuous in the large iliac arteries on the side of the single umbilical artery. In 2 children, aged 18 months and 4 years, atherosclerotic lesions were present in the wide common iliac artery on the side of the obliterated single umbilical artery. These lesions represent the earliest atherosclerotic changes to be found in the human. They are probably related to the remodelling of these arteries, beginning after birth as an adaptation to decreased blood flow.