Absent azygos vein
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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.
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>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>- +<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 href="/articles/intercostal-veins">intercostal veins</a> is ensured by the <a href="/articles/hemiazygos-vein">hemiazygos</a> and <a 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:
- 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. <a href="https://doi.org/10.3348/jksr.2014.70.3.213">doi:10.3348/jksr.2014.70.3.213</a> <span class="ref_v4"></span>
- 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.
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