Fig. 13
From: Angio CT assessment of anatomical variants in renal vasculature: its importance in the living donor
Diagram showing the development of the embryo’s inferior venous system in a 4–6-week embryo and 8–10-week embryo. I-SA: Intersubcardinal anastomoses, S-IA: subcardinal-inferior cardinal anastomoses, MSN: mesonephros, MTN: metanephros, AZG: azygos vein, IV: iliac veins, HZG: hemiazygos vein, AG: adrenal gland, GV: gonadal vein, LV: liver. There are three main venous systems that contribute to the formation of the renal veins and the inferior vena cava. The right subcardinal vein constitutes the suprarenal segment while the I-SA derives into the left renal vein. The hepatic segment forms from the vitelline vein. The azygos and hemiazygos systems are formed from the cranial part of the SPV. The caudal part of the right SPV persists as the infrarenal segment of the IVC. The left subcardinal vein regresses partially, remaining its distal portion as the left gonadal vein. Finally, the persisting segment of the inferior/posterior cardinal veins forms the iliac veins