The lumbar vein (lat. vena lumbalis) is one of two veins that collect blood along the inferior vena cava, which flows into the system of the superior vena cava (other gr. αὐτόϲ - upper, περιφέρω - surround), running parallel along the pedicle of the diaphragm on both its sides, behind the round ligament of the liver and behind the first and second lumbar vertebrae, respectively.
The lumbar vein is a paired vessel, lateral to the sympathetic trunk and the abdominal aorta, located posterior and anterior to the rectus abdominis muscles from the level of the XII thoracic vertebra to the middle of the I lumbar vertebra. Connects the internal iliac vein system with the inferior cava system: it flows from the left side into the left renal vein, from the right into the internal iliac vein[