Adrenal, Renal, Gonadal, Azygos, Hemiazygos, Lumbar, and Ascending Lumbar Veins

The adrenal veins originate during the formation of the prerenal inferior vena cava and are remnants of the caudal portion of the subcardinal veins, cranial to the subcardinal sinus in the embryo. Many have reported variations in the gross appearance of the adrenal veins and their accompanying renal veins. The right renal vein may be doubled, even though the left renal vein is usually single. The left renal may anastomose with the splenic vein and also receive lumbar veins. The ascending lumbar was often variable in its course from pelvic origin to thoracic termination. The gonadal vein may be represented by several vessels or may form a plexus. It may be partially divided into two parts, permitting passage of the gonadal arteries through the cleft vessels. The azygos vein originates in the thorax at the level of the twelfth thoracic vertebra.