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CARDIAC RADIOLOGY Table of Contents   
Year : 2007  |  Volume : 17  |  Issue : 1  |  Page : 50-51
16-MDCT depiction of accessory hemiazygos vein draining into the left brachiocephalic vein


Department of Radiodiagnosis and Imaging, Postgraduate Institute of Medical Education and Research (PGIMER),Chandigarh - 160 012, India

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How to cite this article:
Galwa RP, Prakash M, Khandelwal N. 16-MDCT depiction of accessory hemiazygos vein draining into the left brachiocephalic vein. Indian J Radiol Imaging 2007;17:50-1

How to cite this URL:
Galwa RP, Prakash M, Khandelwal N. 16-MDCT depiction of accessory hemiazygos vein draining into the left brachiocephalic vein. Indian J Radiol Imaging [serial online] 2007 [cited 2019 Sep 19];17:50-1. Available from: http://www.ijri.org/text.asp?2007/17/1/50/32701

   Introduction Top


The venous system may show many variations due to its complex development. Identification and recognition of these venous vessels is important, as they may become dominant vessels if other major veins get obstructed. Contrast enhanced multidetector computed tomography (MDCT) provides fast, noninvasive and comprehensive diagnosis of venous anomalies. [1] We present an uncommon but important venous variant depicted on 16-slice MDCT.


   Case Report Top


A routine contrast-enhanced computerized tomography (CT) scan of the chest and abdomen was performed, on a 35-year-old lady, known to have non-Hodgkin's lymphoma (NHL), to look for residual lymphadenopathy after chemotherapy. On reviewing the axial images, we observed a venous structure on the left side of the posterior mediastinum, which was arching anteriorly over the left lung apex and joining the left brachiocephalic vein. This was the accessory hemiazygos vein draining into the left brachiocephalic vein via the left superior intercostal vein [Figure - 1].

On the right, the azygos vein was seen normally arching anteriorly over the root of the right lung and joining the superior vena cava (SVC) [Figure - 2]. Both subclavian veins, internal jugular veins, brachiocephalic veins, SVC and inferior vena cava (IVC) were normal. The aorta, major arterial branches and pulmonary artery were normal. No mediastinal lymphadenopathy or collateral vessels were seen in the mediastinum.


   Discussion Top


The accessory hemiazygos vein or superior hemiazygos vein is a left thoracic vein which normally drains predominantly the left posterior thoracic cage. [2] It usually courses on the left side of the thoracic vertebral column and joins the azygos vein at the T7 to T8 level by crossing over posterior to the aorta. Sometimes, it can form a common channel with the hemiazygos vein and then drain into the azygos vein. [2] Its tributaries include third to eighth left posterior intercostal veins, mediastinal veins, esophageal veins and sometimes left bronchial veins. The hemiazygos and azygos veins may drain into it. [2] In approximately 75% of cases, a small connection exists between the accessory hemiazygos vein and the left superior intercostal vein but only in 1-2% of cases this communication is large and former drain directly into brachiocephalic vein.

Embryologically, initial venous drainage of the posterior body wall is into the posterior cardinal veins. The drainage is then gradually taken over by the azygos line veins or medial sympathetic line veins on either side. On the left, this leads to the development of the hemiazygos and accessory hemiazygos veins. Initially, the left azygos line vein communicates with the cranial portion of the left posterior cardinal veins, which normally undergo retrogression with persistence of a small portion which develops into the left superior intercostal vein.

Normally, this anomaly is an incidental finding but may become clinically significant in cases of venous obstruction, where it forms a vital collateral pathway. [3],[4] Before the advent of CT and MRI, venography (conventional or digital subtraction) was required to delineate the venous pathways. With advancements in imaging modalities, noninvasive depiction is now easily possible. MDCT imaging with post-processing of acquired data has made possible depiction of normal veins, various venous anomalies and normal variants.

 
   References Top

1.Lawler LP, Corl FM, Fishman EK. Multi-detector row and volume-rendered CT of the normal and accessory flow pathways of the thoracic systemic and pulmonary veins. Radiographics 2002;22:S45-60.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Williams PL, Bannister H, Berry MM, Collins P, Dyson M, Dussek JE, et al. Gray's anatomy. 37 th ed. Churchill Livingstone: New York; 1989. p. 808-10.  Back to cited text no. 2    
3.Ball Jr JB, Proto AV. The variable appearance of the left superior intercostal vein. Radiology 1982;144:445-52.  Back to cited text no. 3    
4.Berk RN. Dilatation of the left superior intercostal vein in the plain-film diagnosis of chronic superior vena caval obstruction. Radiology 1964;83:419-23.  Back to cited text no. 4    

Top
Correspondence Address:
Ram Prakash Galwa
Department of Radiodiagnosis and Imaging, PGIMER, Chandigarh - 160 012
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.32701

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    Figures

  [Figure - 1], [Figure - 2]

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