An absent azygos vein is a very uncommon variant in which the azygos vein fails to develop. In cases of agenesis of the azygos vein, the hemiazygos and accessory hemiazygos veins play an important role in venous drainage, accounting for drainage of both the right and left intercostal veins 1-3.
The variant is exceedingly rare with few cases documented 2.
Absence of the azygos vein occurs due to failure of the superior segment of the right supracardinal vein to develop 3.
Absence of the azygos vein has been documented in the literature to demonstrate aortic nipple on frontal chest radiograph 1,4,5. This is due to enlargement of the left superior intercostal vein owing to increased pressure 1. The shadow of the azygos vein will also be absent 1.
CT will demonstrate an absence of the azygos vein 4.
- 1. Arslan G, Cubuk M, Ozkaynak C, Sindel T, Lüleci E. Absence of the azygos vein. (2000) Clinical imaging. 24 (3): 157-8. doi:10.1016/s0899-7071(00)00191-1 - Pubmed
- 2. Atari M, Nakajima Y, Fukuhara M, Iijima Y, Kinoshita H, Minamiya Y, Uramoto H. An extremely rare case report of surgery of lung cancer with the absence of azygos vein. (2017) Surgical and radiologic anatomy : SRA. 39 (1): 103-106. doi:10.1007/s00276-016-1704-z - Pubmed
- 3. Piciucchi S, Barone D, Sanna S, Dubini A, Goodman LR, Oboldi D, Bertocco M, Ciccotosto C, Gavelli G, Carloni A, Poletti V. The azygos vein pathway: an overview from anatomical variations to pathological changes. (2014) Insights into imaging. 5 (5): 619-28. doi:10.1007/s13244-014-0351-3 - Pubmed
- 4. Yim, Young Hee, Yi, Jeong Geun, Song, In Young, & Park, Jeong Hee (2014). Congenital absence of the azygos vein with persistent left superior vena cava: A case report. Journal of the Korean Radiological Society, 70(3), 213-215.
- 5. Hatfield MK, Vyborny CJ, MacMahon H, Chessare JW. Congenital absence of the azygos vein: a cause for "aortic nipple" enlargement. (1987) AJR. American journal of roentgenology. 149 (2): 273-4. doi:10.2214/ajr.149.2.273 - Pubmed