Which anatomic variations may alter the placement of an inferior vena cava (IVC) filter?

Updated: Oct 31, 2020
  • Author: Gary P Siskin, MD; Chief Editor: Kyung J Cho, MD, FACR, FSIR  more...
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Answer

Answer

Anatomic variations involving the IVC are fairly common in the general population, reflecting variation in the involution and persistence of the cardinal veins. These conditions may be important, because they alter the location of filter deployment in 3-15% of patients. A few of the more common conditions, especially those pertinent to IVC filter placement, are described below.

Duplication of the IVC

Duplication of the IVC is observed in 0.2-3% of individuals. With this anomaly, the left IVC is usually smaller than the right, although they can be equal in size. The left IVC typically empties into the left renal vein (see the following image) and, subsequently, into the right IVC. Although the frequency of duplication is low, demonstration of the anomaly is important when determining the position for IVC filter placement. When the IVC is duplicated, filter placement in the right IVC may not be adequate to prevent PE, especially in the presence of a left lower-extremity DVT. Placement of a filter in both the left and right IVCs is often required for true PE prophylaxis in the patient with a duplicated IVC. The filter may also be placed suprarenally.

Anteroposterior image from an inferior venacavogra Anteroposterior image from an inferior venacavographic examination demonstrates duplication of the inferior vena cava. The left-sided inferior vena cava drains into the left renal vein.

Transposition of the IVC

Transposition of the IVC is observed in 0.2-0.5% of individuals. A left-sided IVC drains into the left renal vein and crosses to the right of the spine. It then continues cranially in the normal position. The left renal and suprarenal veins empty directly into the left IVC; the right gonadal and suprarenal veins drain into the right renal vein and, subsequently, into the normal right-sided prerenal division of the left-sided IVC.

Circumaortic and retroaortic left renal vein

The incidence of circumaortic renal veins has been reported to be as high as 8.7% (see the image below). Patients with circumaortic or multiple renal veins may have a large hilar communication, which provides an alternative conduit for emboli. In the presence of a circumaortic renal vein, a filter immediately inferior to the main left renal vein may not represent adequate prophylaxis because of the alternative conduit; therefore, filters should be positioned inferior to the circumaortic renal vein. A retroaortic left renal vein is more common but does not impact filter placement, because it does not represent a potential conduit for thrombus arising from the lower extremities.

Anteroposterior image from an inferior venacavogra Anteroposterior image from an inferior venacavographic examination demonstrates a circumaortic left renal vein.

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