An abnormal course of the interazygos vein: a case report
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(2020) 14:232
CASE REPORT
Open Access
An abnormal course of the interazygos vein: a case report Elham Shiri1 and Soheila Madadi2*
Abstract Background: The azygos venous system in the posterior mediastinum has a complex developmental pattern. Case presentation: During the dissection of this region, we encountered a variation in this system. In this case, we observed that the accessory hemiazygos and hemiazygos veins in the left side passed anterior to the aorta and drained to the azygos vein located on the left side of the vertebral column. Other structures were normal in this area. Conclusions: This variation is important in mediastinal surgery and radiographic interpretation. Keywords: Variation, Azygos vein, Hemiazygos vein, Accessory hemiazygos vein, Preaortic interazygos vein
Introduction The posterior intercostal veins drain the thoracic wall. On the two sides of the thorax, the first posterior intercostal vein directly drains into the brachiocephalic vein. The second and third and occasionally fourth intercostal veins join together to form the superior intercostal vein, which drains into the brachycephalic vein on the left side and into the azygous vein on the right side. On the left side, the fourth or fifth to eighth intercostal veins drain into the accessory hemiazygos vein, and the three lower intercostal veins (9th to 11th) also drain into the hemiazygos vein. On the right side, the remaining posterior intercostal veins (seven or eight lower intercostal veins) drain into the azygos vein [1]. Accessory hemiazygos and hemiazygos veins pass posterior to the aorta to drain into the azygos vein. Because of the complex embryologic development of these veins, many possible variations may be expected to occur [2, 3]. The most common congenital abnormalities include agenesis of the azygos vein, azygos continuation of the inferior vena cava, an azygos lobe of the right lung, and partial venous
return [4]. If one of these veins crosses the ventral aspect of the aorta, this may lead to misinterpretation of computed tomographic (CT) and magnetic resonance imaging (MRI) scans [5–8]. In the present case report, we describe a rare variation of the azygos venous system and discuss its clinical importance.
Case presentation During the dissection of the thoracic part of a 70-yearold Iranian male cadaver, a variation of the azygos venous system was observed. The hemiazygos and accessory hemiazygos veins passed ventral to the aorta. These veins crossed ventral to the aorta to open into the azygos vein on the right side. The azygos vein was located on the left side of the vertebral column, then, at the top, it moved toward the right side of the vertebral column to drain into the superior vena cava vein. Also, we encountered an enlarged heart. No other abnormalities were observed. The various arrangement of these veins is shown in Figs. 1 and 2.
* Correspondence: [email protected]; [email protected] 2 Department of Anatomy, School of Medicine, Arak University of Medical Sciences, Arak, Iran Full list of auth
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