The Impact of Aging on the Anatomical Course of the Azygos Vein: A Retrospective, Computed Tomography Study

The azygos vein (AV) is typically described as ascending vertically to the right of the vertebral column before arching anteriorly to drain into the superior vena cava. However, a small number of studies suggest that it is found leftward in older adults. A retrospective analysis of the contrast-enhanced thoracic computed tomography studies from 291 individuals was conducted with ethical approval (158 females; ages 0-100). The vertebral level (VL) of the AV arch was designated "V0" with subsequent caudal VLs designated V1-V5. At each VL, the position of the AV and thoracic aorta (TA) relative to the vertebral midpoint was recorded in degrees. A significant correlation was found between increasing age and leftward shift of the AV and aorta between V0 and V4 (Spearman's ρ correlation between 0.31 and 0.68, p < 0.001). At V5, while AV position no longer changed with age (ρ = -0.03, p > 0.05), TA shift persisted (ρ = 0.39, p < 0.001). Increased positional variability of AV with age was also observed at V1-V5 (ρ between 0.17 and 0.38, p < 0.05). This leftward shift of AV and TA could reflect age-related laxity of the posterior mediastinum or relative reduction in the VC height. Understanding of this age-related anatomical change is important for reducing the risk of vascular injury during thoracic procedures. As inclusion of age-related changes is becoming increasingly important in undergraduate anatomy teaching, our findings suggest that it may be necessary to update current texts.