Interrupted IVC with Azygos Vein Continuation
(Right supracardinal vein > Azygos vein)
Bilateral IVC
Both images above are from Netter's Atlas
(From Tal Geva. Anomalies of Systemic Veins chapter in Moss & Adams 8th ed. Page 856)
Some images worth learning from are posted here (Note: Most of them are plagiarised. But, sources are referenced)