Azygos vein

Arslan G., Cubuk M., Ozkaynak C., Sindel T., Luleci E. (2000) Absence of the azygos vein. Clin Imaging 24 157-158. 

Delayed catheter migration can be caused by head or arm motion, coughing or simply assuming the erect position (Nazarian et al. 1997) (Fig. 6.12). Catheters originally placed within the right atrium can migrate into the IJV,the azygos vein, or the contralateral bra-... 

Then the pericardium is incised over the superior vena cava (SVC) and the vein is dissected circumferentially. Here, care has to be taken not to injure the azygos vein and the sinoatrial node. A suture is passed around the SVC but not tied. Next, the inferior vena cava (IVC) is circumferentially freed from the pericardial reflection. 

Four main groups of collateral thoracic veins include azygos system of veins -communication between SVC and ascending lumbar vein subfascial system of epigastric veins - collateral circulation between brachiocephalic vein and external femoral vein subcutaneous system of superficial epigastric vein and vertebral veins. Less frequently, systemic-pulmonary or intramuscular pathways are involved. 

Subfascial veins connect external iliac vein and subclavian vein via internal thoracic and inferior epigastric veins. Internal thoracic veins (TTV) are tributaries of brachiocephalic veins. They are formed by junction of musculophrenic veins and superior epigastric veins. Internal thoracic veins anastomose at the posterior surface of sternum. Parietal tributaries of ITV are anterior intercostal veins, which provide anastomosis with the azygos sysem, by means of posterior intercostals. Additional tributaries of brachiocephalic veins, frequently widened in patients with SVC syndrome, are pericardiophrenic veins. 

Fig. 1. Azygos system of veins. Multiple anastomoses of this system include parietal veins (lumbar, ascending lumbar, intercostal, -superior phrenic) as well as visceral ( -renal, -mediastinal, including bronchial, esopahgeal, pericardiac) veins.

Fig. 2. Curved multiplanar reformation. Widening of azygos sytem of veins in a patient with left-sided SVC syndrome.

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