The complete anatomy of the azygos vein: a meta-analysis with clinical implications.

Abstract

Background: The azygos vein (AV) plays a crucial role in the mediastinal region, exhibiting considerable variability in its anatomy and relationship with surrounding structures. This study aims to assess the morphometry and anatomy of the AV through a comprehensive meta-analysis of studies reporting extractable data on this vessel.

Materials and methods: Major online medical databases such as PubMed, Scopus, ScienceDirect, Web of Science, SciELO, BIOSIS, Current Content Connect, Korean Journal Database and Wiley online library were searched to gather all relevant studies regarding the anatomical characteristics of the AV.

Results: The results of the present meta-analysis comprised 40 studies, categorized into eight groups for data analysis. The mean AV diameter at its origin was set at 3.86 mm (SE = 0.84). The most prevalent was type IIB, with a prevalence of 40.23% (95% CI: 29.06-51.92%). The pooled prevalence of the right subcostal and right ascending lumbar veins forming the AV was 73.82% (95% CI: 55.77-88.67%).

Conclusions: The AV exhibits a high degree of variability regarding its origin, trajectory, and connections with the hemiazygos system. The most prevalent type of AV, according to the Anson and McVay classification, was Type II (transitional type). Moreover, the vein was found to be formed by the right subcostal and the right ascending lumbar veins in the majority of the cases. This is the most comprehensive and current assessment of AV morphometry and anatomy to date. The findings are a valuable resource for physicians, especially surgeons performing various procedures in the mediastinum.