Azygos ladder and looped thoracic duct – a case report

The azygos vein is the vein that drains the thoracic wall and upper lumbar region. It is the important channel connecting the two venae cavae. Its origin is variable. On developmental grounds it should originate from the posterior surface of the inferior vena cava near the renal veins. This is known as lumbar azygos vein. In the absence of lumbar azygos, it is formed by the union of ascending lumbar vein with the right subcostal vein at the T12 vertebra. The azygos vein enters the thorax either by piercing the right crus of the diaphragm or by passing through the aortic opening of the diaphragm. It ascends vertically in the posterior mediastinum in front of the lower 8 thoracic vertebrae. At the level of the T4 vertebra, it arches forwards over the root of right lung and terminates by opening into the superior vena cava. It receives the accessory hemiazygos and hemiazygos veins, right superior intercostal vein, and 5th to 11th posterior intercostal veins of right side. It also receives bronchial, esophageal, pericardial and mediastinal veins. The thoracic duct is the largest lymphatic channel of the body. It drains the lymph from the both halves of the body below the diaphragm and the left half of the body above the diaphragm. It begins as the continuation of the cisterna chyli near the lower border of T12 vertebra and enters the thorax by passing through the aortic opening. It ascends up in the posterior mediastinum between azygos vein and descending thoracic aorta, behind the esophagus. It crosses from right to left side at the level of T5 vertebra and ascends in the superior mediastinum to reach the neck. In the neck it arches laterally at the level of the transverse process of C7 vertebra and ends by opening into the junction between left subclavian and internal jugular veins. We noted the variations of azygos system of veins and thoracic duct, which are of importance to surgeons and radiologists.