Azygos vein of posterior thoracic wall

Azygos vein of posterior thoracic wall

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Location

It is present only on the right side in the upper abdominal wall

Tributaries

·         Right ascending lumbar vein

·         Right subcostal vein

·         Right superior intercostals vein (created by 2-4^th right posterior intercostals veins

·         Hemiazygos vein

·         Accessory hemiazygos vein

·         Right brochial veins

·         Esophageal veins

·         Mediastinal veins

·         Pericardial veins 

Formation

Its formation is variable:

1.    It is formed by the union of the ascending lumbar veins with the right subcostal veins at the level of the 12th thoracic vertebra, 

2.    Arises from the posterior aspect of the inferior vena cava near the renal veins

3.    As a continuation of right subcostal vein

4.    Occationally it may arise from the right renal or right first lumbar vein

Course

 It enters the thorax via the aortic hiatus in the diaphragm and ascends posteriorly alongside the vertebral bodies, arching over the right main bronchus at T5-T6 and enters the superior vena cava (SVC) at T4 

Variant anatomy

The azygos vein may rarely drain into the right brachiocephalic vein, right subclavian vein, intrapericardial SVC or directly into the right atrium

Drainage area

Thoracic wall and upper lumbar region