ANSWER: Circumaortic left renal vein
EXPLANATION:
The circumaortic left renal vein (LRV) is the most common inferior vena cava (IVC) congenital anomaly, and is defined as a separate venous communication from the anterior main left renal vein coursing posterior to the abdominal aorta and anastomosing with the IVC inferiorly.
There are 3 anatomic categories of congenital IVC anomalies:
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Infrarenal: duplicate IVC, pre-aortic IVC, persistent left sided IVC, and absence of the infrarenal IVC.
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Renal: accessory left renal vein, circumaortic left renal vein, and retroaortic left renal vein.
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Suprarenal: absence of the hepatic IVC with azygous continuation, IVC membranes, and congenital caval stenosis/atresia.
WRONG ANSWERS:
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Duplicated IVC: an additional left-sided superior vena cava (SVC) that drains into the LRV and either anastomoses with the left common iliac vein from the right-sided IVC or have its own left common iliac vein branch. Filtration in this scenario is performed with a suprarenal vena cava filter or a filter in each of the IVCs.
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Left-sided IVC: there are variable definitions/iterations, however characteristically the infrarenal IVC courses to the left of the abdominal aorta. No special consideration is needed for placement.
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Retroaortic LRV: the main LRV courses posterior to the aorta instead of the normal anterior location. No special consideration is needed for placement.
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Accessory LRV: similar to the circumaortic LRV, however the additional LRV runs anterior to the aorta and parallel to the main LRV. Filter placement location is similar to that of circumaortic LRV
REFERENCES:
Alkhouli M, Morad M, Narins CR, Raza F, Bashir R. Inferior Vena Cava Thrombosis. JACC Cardiovasc Interv. 2016;9(7):629-643.
Binkert, Christoph A. “Chapter 104: Caval Filtration.” Image Guided Interventions, by Matthew A. Mauro, et al.; 2nd ed., Saunders Elsevier, 2014, pp. 781-789.
