Absent azygos vein

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~~The~~An ~~absence of the~~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.

Epidemiology

The variant is exceedingly rare with few cases documented ².

Clinical presentation

Presentation is asymptomatic as drainage of the intercostal veins is ensured by the hemiazygos and accessory hemiazygos veins ³.

Pathology

Absence of the azygos vein occurs due to failure of the superior segment of the right supracardinal vein to develop ³.

Radiographic features

Plain radiograph

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

CT will demonstrate an absence of the azygos vein ⁴.

-<p>The <strong>absence of the azygos vein</strong> is a very uncommon variant in which the <a title="Azygos vein" href="/articles/azygos-vein">azygos vein</a> fails to develop. In cases of agenesis of the azygos vein, the <a href="/articles/hemiazygos-vein">hemiazygos</a> and <a href="/articles/accessory-hemiazygos-vein">accessory hemiazygos</a> veins play an important role in venous drainage, accounting for drainage of both the right and left <a href="/articles/venous-drainage-of-the-thoracic-wall">intercostal veins</a> <sup>1-3</sup>.</p><h4>Epidemiology</h4><p>The variant is exceedingly rare with few cases documented <sup>2</sup>. </p><h4>Clinical presentation</h4><p>Presentation is asymptomatic as drainage of the intercostal veins is ensured by the hemiazygos and accessory hemiazygos veins <sup>3</sup>. </p><h4>Pathology</h4><p>Absence of the azygos vein occurs due to failure of the superior segment of the right supracardinal vein to develop <sup>3</sup>. </p><h4>Radiographic features </h4><h5>Plain radiograph</h5><p>Absence of the azygos vein has been documented in the literature to demonstrate <a href="/articles/aortic-nipple">aortic nipple</a> on frontal chest radiograph <sup>1,4,5</sup>. This is due to enlargement of the <a href="/articles/left-superior-intercostal-vein">left superior intercostal vein</a> owing to increased pressure <sup>1</sup>. The shadow of the azygos vein will also be absent <sup>1</sup>.</p><h5>CT</h5><p>CT will demonstrate an absence of the azygos vein <sup>4</sup>. </p>
+<p>An <strong>absent azygos vein</strong> is a very uncommon variant in which the <a href="/articles/azygos-vein">azygos vein</a> fails to develop. In cases of agenesis of the azygos vein, the <a href="/articles/hemiazygos-vein">hemiazygos</a> and <a href="/articles/accessory-hemiazygos-vein">accessory hemiazygos</a> veins play an important role in venous drainage, accounting for drainage of both the right and left <a href="/articles/venous-drainage-of-the-thoracic-wall">intercostal veins</a> <sup>1-3</sup>.</p><h4>Epidemiology</h4><p>The variant is exceedingly rare with few cases documented <sup>2</sup>. </p><h4>Clinical presentation</h4><p>Presentation is asymptomatic as drainage of the <a title="intercostal veins" href="/articles/intercostal-veins">intercostal veins</a> is ensured by the <a title="Hemiazygos vein" href="/articles/hemiazygos-vein">hemiazygos</a> and <a title="Accessory hemiazygos vein" href="/articles/accessory-hemiazygos-vein">accessory hemiazygos veins</a> <sup>3</sup>. </p><h4>Pathology</h4><p>Absence of the azygos vein occurs due to failure of the superior segment of the right supracardinal vein to develop <sup>3</sup>. </p><h4>Radiographic features </h4><h5>Plain radiograph</h5><p>Absence of the azygos vein has been documented in the literature to demonstrate <a href="/articles/aortic-nipple">aortic nipple</a> on frontal chest radiograph <sup>1,4,5</sup>. This is due to enlargement of the <a href="/articles/left-superior-intercostal-vein">left superior intercostal vein</a> owing to increased pressure <sup>1</sup>. The shadow of the azygos vein will also be absent <sup>1</sup>.</p><h5>CT</h5><p>CT will demonstrate an absence of the azygos vein <sup>4</sup>. </p>

References changed:

1. Arslan G, Cubuk M, Ozkaynak C, Sindel T, Lüleci E. Absence of the azygos vein. (2000) Clinical imaging. 24 (3): 157-8. <a href="https://doi.org/10.1016/s0899-7071(00)00191-1">doi:10.1016/s0899-7071(00)00191-1</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/11150683">Pubmed</a> <span class="ref_v4"></span>
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. <a href="https://doi.org/10.1007/s00276-016-1704-z">doi:10.1007/s00276-016-1704-z</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/27262308">Pubmed</a> <span class="ref_v4"></span>
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. <a href="https://doi.org/10.2214/ajr.149.2.273">doi:10.2214/ajr.149.2.273</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/3496750">Pubmed</a> <span class="ref_v4"></span>
1.Gökhan Arslan, Metin Çubuk, Can Özkaynak, Timur Sindel, Ersin Lüleci, Absence of the azygos vein, Clinical Imaging, Volume 24, Issue 3, 2000, Pages 157-158, ISSN 0899-7071, https://doi.org/10.1016/S0899-7071(00)00191-1. (https://www.sciencedirect.com/science/article/pii/S0899707100001911)
2. Atari M, Nakajima Y, Fukuhara M, Iijima Y, Kinoshita H, Minamiya Y, et al. An extremely rare case report of surgery of lung cancer with the absence of azygos vein. Surgical and Radiologic Anatomy. 2017;39(1):103-6.
5. Hatfield MK, Vyborny CJ, MacMahon H, Chessare JW. Congenital absence of the azygos vein: a cause for "aortic nipple" enlargement. AJR Am J Roentgenol. 1987 Aug;149(2):273-4. doi: 10.2214/ajr.149.2.273. PMID: 3496750.