Mesoaortic entrapment of a left inferior vena cava.

A persistent left inferior vena cava (IVC) is a rare anomaly, with a reported incidence of only 0.2-0.5%. When present, it courses between the superior mesenteric artery and the aorta to continue as the right IVC, similar to the course of a left renal vein (LRV). This anomaly is usually asymptomatic, but there may be vague abdominal complaints if the IVC is compressed in the mesoaortic angle. Although symptomatic compression of the LRV (anterior nutcracker syndrome) is well recognized, there has been only one report in the literature of a similar compression of a persistent left IVC. Because of its rarity, this anomaly may be missed or mistaken for other conditions on imaging. An accurate diagnosis is crucial as the presence of this anomaly may have implications for surgical treatment of aortic lesions or placement of an IVC filter. Magnetic resonance angiography and, more recently, multidetector computed tomography scan, can provide an exquisite three-dimensional demonstration of vascular abnormalities.