[Straight azygos continuation of the inferior vena cava. Apropos of 3 cases using an NMR study].

Three patients with straight azygos vein continuation of inferior vena cava (IVC) were studied by nuclear magnetic resonance (NMR) imaging. In all three cases the diagnosis had been established previously by ultrasound and/or computed tomography imaging, but NMR images provided better anatomical precision of the venous anomaly : visualization of the total trajectory of the major azygos vein, the caliber of which can exceed that of aorta, and absence of retrohepatic segment of IVC but presence of a short supradiaphragmatic segment towards which converge the suprahepatic veins; anastomotic etwork between IVC and major azygos vein contributing to ensure continuity of venous drainage superior to its renal segment. The advantages of NMR are described and the precise diagnostic role of this new method of imaging in the diagnosis of this type of anomaly discussed.