An Anomalous Single Azygos-Hemiazygos Vein Associated with Retro-Aortic Left Renal and Accessory Renal Veins *

Anomalies of the venous system are known to be varied and frequent and, therefore, are often taken for granted. Perhaps for that reason we have been unable to discover in the literature an adequate description of a single midline vein receiving the drainage usually cared for by the azygos and hemiazygos systems. The condition has been observed previously, for in Piersol's Human Anatomy (1936, p. 896) is the statement: "More rarely the two veins (azygos and hemiazygos)t have been observed fused to form a single trunk lying upon the anterior surface of the thoracic vertebrae and receiving all the intercostal veins." A similar record, likewise with no reference to the source of the information, is found in Morris' Human Anatomy (1933, p. 736): "The method of termination of the intercostal veins on the left side is subject to such variation that a normal arrangement can scarcely be said to exist at all. The eighth may open directly into the azygos, as may the seventh and ninth or even more or all of the veins; the hemiazygos and accessory hemiazygos veins may thus be very limited in extent or even be altogether absent." Again, in Cunningham's Textbook of Antomy (1937, p. 1242): "The superior and inferior hemiazygos veins may be absent. In such cases each left intercostal vein opens separately into the vena azygos." And in the same text (p. 1292): "The transverse parts of the hemiazygos veins are remnants of the intermediate part of the subvertebral plexus; they are occasionally connected together by a median anastomosis which represents part of a precentral vein." With these exceptions, no description of the anomaly to be described below has come to our attention in a survey of the Concilium Bibliographicum and of the Cumulative Index Medicus for the years subsequent to the cessation of publication of the Concilium.