The early embryologic cardinal, vitelline, and umbilical veins initially develop from capillary plexuses and ultimately drain into the sinus venosus. The anterior and posterior cardinal veins run cranially and caudally to the heart, later developing into the superior vena cava (SVC) and inferior vena cava (IVC), respectively. The posterior cardinal veins regress, and the subcardinal and supracardinal veins arise. The right supracardinal vein drains the lower abdomen, including what will ultimately become the renal and gonadal veins (Figs. 80.1 and 80.2) in gestational weeks 5–7, into the iliac anastomosis (Mozes and Gloviczki 2007; Nallikuzhy et al. 2018; Kara et al. 2012).