Case Presentation. A 79-year-old female presented with pain and swelling of the left lower extremity. Physical examination revealed a swollen left calf and 1+ pitting edema over both ankles. There was no evidence of calf tenderness and Homan’s sign was negative bilaterally. A venous duplex Doppler study revealed the presence of occluding thrombi in the left popliteal, as well as the right popliteal and posterior tibial veins. She was also found to have microcytic hypochromic anemia. Upper gastrointestinal endoscopy revealed the presence of erosive esophagitis and antral gastritis. Due to the increased risk of gastrointestinal bleeding on warfarin therapy, placement of an inferior vena cava (IVC) filter was advised.

Figure 2.

Venogram demonstrating left-sided inferior vena cava.

Figure 1.

Filter in the right-sided inferior vena cava.

       The initial venogram was performed through a right femoral venous sheath. The inferior vena cava was noted to be smaller in caliber than usual. Previously performed abdominal computed tomography (CT) scans of the abdomen had not indicated the presence of any retroperitoneal masses or a duplicate IVC. AGunther-Tulip filter was deployed in the inferior vena cava, just caudal to the right renal vein (Figure 1). The subsequent completion venogram revealed faint filling of a leftsided IVC. This structure had been mistaken for the left renal vein in the first venogram. The previously performed abdominal CT scans were urgently reviewed with a radiologist. These CT scans suggested the presence of a duplicate IVC. Hence, a sheath was placed in the left femoral vein and another venogram was performed (Figure 2), which outlined the left limb of the duplicate IVC. Both limbs of the IVC joined at the level of the renal veins. No infrarenal interiliac communicating vein was identified. Since the patient had bilateral deep vein thrombosis, a second Gunther- Tulip filter was deployed in the left limb of the IVC, just caudal to the left renal vein (Figure 3).

Figure 3.

Filter in left-sided inferior vena cava.

       Discussion. The incidence of duplicate IVC varies between 0.39 to 3%.^1,2 The inferior vena cava develops from three sets of paired venous channels that appear between the sixth and tenth weeks of gestation. A duplicate IVC results from the failure of regression of the left supracardinal vein. The left and right inferior vena cavas join at the level of the renal arteries to form the suprarenal IVC. Often, the two infrarenal vena cavas also communicate through an interiliac communicating vein.
       During IVC filter placement, a duplicate IVC should be suspected if the IVC appears to be unusually small in caliber on the initial venogram. In addition, the venogram may also uncover an interiliac communication and subsequent filling of the contralateral IVC. In cases of bilateral DVT, or in the presence of a large interiliac communicating branch, filter deployment would need to be considered in both limbs of the infrarenal IVC. If one of the limbs is felt to be too small in caliber, a suprarenal stent deployment may be considered.³
       Clinically, a duplicate IVC should be considered in the event of recurrent pulmonary embolism after the placement of an IVC filter. Venography is considered to be the gold standard for the diagnosis of anomalies of the IVC. CT and magnetic resonance imaging may occasionally mistake the duplicated IVC for lymph nodes or other retroperitoneal structures.⁴