Congenital anomalies of the inferior vena cava (IVC) are rare anatomic variants that include double IVC, left-sided IVC and two anatomic variants of the renal vein (retroaortic left renal vein and circumaortic left renal vein). The development of the IVC starts in the sixth week of gestation, when the posterior cardinal veins appear with the subcardinal veins. Posterior cardinal veins then regress, except the distal part such as iliac vessels. Subcardinal veins form the suprarenal IVC and supracardinal veins form the infrarenal IVC. The left side of both systems regresses. The subcardinal and supracardinal systems create an anastomosis at the level of the renal vessel system. Anomalies of the IVC occur due to its complex embryogenetic processes. These anomalies are an important aspect of aortoiliac surgery, nephrectomy, kidney transplantation and interventions such as IVC filter. Left-sided IVC has a reported incidence of 0.2%–0.5% [1,2]. Furthermore case of abdominal aortic aneurysm with left-sided IVC is very rare. It often crosses the anterior portion of aorta at the level of the renal vessels. In this article, we report two cases of open abdominal aortic aneurysm repair with associated left-sided IVC.

Case 1: The patient was a 69-year-old man who had hypertension, diabetes mellitus and a history of stroke. He underwent laparoscopic wedge resection due to gastrointestinal stromal tumor. On abdominal CT scan before laparoscopic surgery, an abdominal aortic aneurysm (AAA) was diagnosed. The initial diameter of AAA was less than 5 cm; however, during follow-up, its size increased to 6 cm. Also, left-sided IVC was detected on CT angiography (Fig. 1). A long midline incision was made and open repair of the AAA was conducted by a transperitoneal approach. At the level of the renal artery, left-sided IVC was revealed, crossing over the neck of the aorta (Fig. 2). After dissection between the aortic neck and the crossing IVC, the aorta was clamped at the infrarenal portion. Aorto-biiliac anastomosis was performed with a Dacron bifurcated graft. The patient was discharged on postoperative day 8 without any major complications.

Figure 1. Transverse and coronal view CT (Case 1). The contour of left-sided IVC is marked with a white arrow. The abdominal aortic aneurysmal sac is adjacent to the left-sided IVC. In this case, the neck of the aneurysmal sac is below the left-sided IVC such that the surgical field is sufficient for vascular anastomosis.

Figure 2. Surgical findings of Case 1. Left-sided IVC (white arrow) crossing over the proximal neck (asterisk mark) for anerusymal neck-area of the AAA.

Case 2: A 65-year-old man who had hypertension, diabetes mellitus, dyslipidemia and gout was diagnosed with AAA on his regular medical check-up. After 1-year of follow-up, its size had grown from 4 to 5.7 cm (Fig. 3) and a surgical repair was scheduled. The aortic aneurysm was identified through a transperitoneal approach with a long midline incision. There was severe adhesion between the aneurysm and left-sided IVC.

Figure 3. Transverse and coronal view CT (Case 2). The contour of left-sided IVC is marked with a white arrow.

Thus, we did not separate the IVC from the aneurysmal sac. Lifting the crossing portion of IVC, proximal anastomosis of the aneurysmal neck was performed. Because the distal margin of the aneurysm did not reach at the iliac bifurcation, a Dacron tube graft 20 mm in diameter was used to reconstruct the aorta. The patient was discharged on postoperative day 7 without any major complications (Fig. 4).

Figure 4. Surgical findings of Case 2. (A) Left-sided IVC (white arrow). (B) Aneurysmal neck (proximal) before anastomosis. (C) Aneurysmal neck (proximal) after anastomosis. (D) Vascular anastomosis was performed with a 20-mm Dacron tube graft.

Anatomical variants of IVC are a rare phenomenon originating from complicated embryologic processes in the first trimester of gestation [3]. It occurs when the three primitive components (postcardinal, subcardinal and supracardinal systems) do not unite and regress appropriately. Variants of the inferior vena cava consist of duplication of the IVC, left-sided IVC, retro-aortic left renal vein and circumaortic renal collar. Duplication of the IVC and left-sided IVC are major anomalies of IVC [4]. The reported incidence of left-sided IVC is 0.2% to 0.5% [1,2]. It is often diagnosed preoperatively, during the work-up for aortoiliac surgery. CT is considered the gold standard for diagnosing anomalies of the IVC [5,6].

As other researchers reported cases of IVC anomalies during aortoiliac surgery [7-9], we performed two cases of elective AAA repair with a transperitoneal approach. The proximal neck can be far below the vascular anastomosis, or near the left-sided IVC crossing above the abdominal aorta. Our two cases represented these two situations encountered during open repair of AAA. As mentioned in other case reports, with adequate IVC dissection and mobilization, a sufficient surgical field for proximal neck approach can be achieved [7]. Before AAA repair, the level of the proximal neck of the aneurysm should be assessed to ensure that it is not too high for vascular anastomosis.

In conclusion, left-sided IVC is a rare anomaly of the IVC. The crossing portion of the IVC above the abdominal aorta can cause difficulties during AAA repair. Appropriate evaluation of the proximal neck of the aneurysm should be performed before surgery.

The authors declare no conflicts of interest.