|
| Possible mechanism |
Group I | Figure 1(a) | Unilateral right-sided single preureteric vena cava. Persistence of the right postcardinal vein, disappearance or failure of development of the right supracardinal vein. |
Group II | Figure 1(b) | Unilateral right-sided double Inferior Vena Cava. Ureter between the two veins. Persistence of the right supracardinal vein and of the right postcardinal vein. |
Group III | Figure 1(c) | Bilateral, single Inferior Vena Cava, the right being preureteric and the left postureteric. Persistence of the right postcardinal vein and the left supracardinal vein. |
Group IV | Figure 1(d) | Bilateral single preureteric Inferior Vena Cava. Persistence of the right and left postcardinal veins. |
Group V | Figure 1(e) | Double right vena cava, ureter between the two veins, single postureteric left vena cava. Persistence of the right supracardinal and postcardinal veins as well as of the left supracardinal vein. |