Vena cava variations

The figures illustrate the various anomalies that have been reported for the inferior vena cava, the most common of which is the circumaortic left renal vein.
(A) Partial malrotation and left IVC (prevalence: 0.2 to 0.5%).
(B) Duplicated IVC with left IVC draining into the left renal vein (prevalence: 0.2 to 0.3%).
(C) Azygos communication with the IVC; lack of continuity between the prerenal segment of the IVC and the hepatic segment (prevalence: 0.6%).
(D) Circumaortic left renal vein (renal vein collar, double left renal vein) (prevalence as high as 8.7%).
(E) Retroaortic left renal vein (prevalence about 2.0%).
(F) Double IVC with hemiazygos continuation of the right IVC (case reports).
(G) Double IVC with retroaortic left renal vein and azygos communication with the right IVC; lack of continuity between the prerenal segment of the IVC and the hepatic segment (case reports).
(H) Circumcaval ureter. Usually occurs on the right (case reports).
(I) Absent infrarenal IVC; paravertebral collateral veins communicate via the azygos vein.