Fig. 1
From: Congenital systemic venous return anomalies to the right atrium review
Normal systemic venous system schematic. The typical systemic venous system consisting of the right-sided superior vena cava, result of the confluence of the brachiocephalic veins, and the right-sided inferior vena cava (IVC), formed by the confluence of the common iliac veins, which respectively, drain the venous blood from the upper and lower body to the right atrium. Due to its particular embryology and relationship with the abdominal organs, the IVC can be subdivided in different segments (suprahepatic, hepatic, suprarenal, renal, infrarenal segments) and is asymmetric, with the gonadal and suprarenal veins draining directly into it on the right but to the left renal vein, instead, on the left. The azygos-hemiazygos venous system, running on the side of the vertebral column, drains the thoracic wall and superior lumbar region into the superior vena cava via the arch of the azygos vein