Azygography.

Abstract

Though the azygos system is an important anastomotic channel between the superior and inferior venae cavae, little attention has been paid to it and to its intimate relation to the paravertebral veins. The arch of the azygos vein is often seen on the postero-anterior film of the chest and, according to Burke (2), was described by Nuvoli on frontal tomograms. Fleischner (5) mentioned its dilatation in congestive failure and Ellis (4) discussed possible confusion with more significant shadows. Stauffer (10) succeeded in catheterizing the azygos vein in 1951, and in the same year Mellins (9) showed free communication between the femoral and azygos veins when contrast material was injected through a catheter in the saphenous vein. Lessmann (7, 8) and Tori (12) give credit for successful intraosseous venography to Erhardt and Kneip in 1943. Drasnar (3) in 1946 reported on infusions and transfusions by way of the bone marrow and stated that he had performed intraosseous venography in 1942. Lessmann's work included intracostal venography. Tori (12) and Süsse (11) wrote exclusively on azygos opacification. The former injected the thoracic spinous processes, a technic which clearly showed the communication between the paravertebral and azygos systems, though in our hands it met with inconsistent results. Süsse reported on intracostal injection and mentions that Fischgold and Prospenzi had used thoracic spinous processes and Prospenzi and Ficara had also injected ribs. Other papers on this subject, appearing in the foreign literature, are not readily available. The azygos vein begins adjacent to the first or second lumbar vertebra as a continuation of the ascending lumbar vein. It enters the thorax through the aortic hiatus and arches forward at the fourth thoracic vertebra, over the root of the right lung, to enter the superior vena cava. On its right, it receives the subcostal and intercostal veins, the upper three or four of the intercostal veins draining by a common trunk, the superior intercostal vein. The left intercostals communicate with the azygos via the accessory hemiazygos and hemiazygos veins. The hemiazygos, the thoracic continuation of the left ascending lumbar vein, receives the lower four or five intercostal veins, and empties into the azygos at the level of T-9. The accessory hemiazygos is made up by the confluence of intercostal veins between T-3 and T-9. It drains into the azygos or hemiazygos at T-8. This anatomical description is taken from Gray (6) and corresponds to that of other texts. It appears to be stylized. We have not consistently produced opacification of the accessory hemiazygos and hemiazygos and have shown intercostal veins that are supposed to communicate with the hemiazygos draining directly into the azygos. In addition, the thoracic portion of the azygos often appears to be much further to the left than has been indicated (Fig. 1).