Venous Anomalies Encountered During Aortic Reconstruction

John J. Ricotta and Wadi Gomero-Cure

During the first trimester of embryologic development, the inferior vena cava (IVC) and renal veins develop from three paired venous channels that normally undergo fusion followed by partial regression, resulting in the formation of several anastomoses. This complex process can give rise to several anomalies of the IVC and renal veins that, albeit rare, will likely be encountered at some point by most practicing vascular surgeons. The most relevant anatomic variations are retroaortic left renal vein (LRV), circumaortic LRV or venous collar, complete duplication of the IVC, and transposed or left-sided IVC. These anomalies are important because of the potential they pose for inadvertent venous injury and massive hemorrhage during aortic dissection or clamping during open aortic reconstruction.

Venous hemorrhage is a troublesome and potentially fatal intraoperative complication of open aortic surgery. Careful preoperative assessment with contrast-enhanced computed tomography (CT) scan or magnetic resonance imaging (MRI) can diagnose most common venous anomalies at risk for injury. Nevertheless, preoperative imaging might not demonstrate all anomalies and is not routinely used on all patients. Thus, intraoperative recognition of aberrancies in venous anatomy is incumbent upon the surgeon.

Retroaortic or Circumaortic Left Renal Vein

The LRV is an important landmark during open aortic surgery. When it is not found in its normal ventral location anterior to the aorta and posterior to the superior mesenteric artery on preoperative imaging or intraoperative assessment, the surgeon should consider the possibility of a retroaortic venous anomaly. Retroaortic LRV (Figure 1) is seen in approximately 2% of patients and is in itself clinically insignificant. The anomalous renal vein typically courses caudally behind the aorta to enter the IVC at the level of the inferior mesenteric artery. Even when a normal-appearing LRV is seen ventral to the aorta on preoperative imaging or intraoperatively, the presence of structures posterior to the aorta can suggest posterior venous components and possibly a circumaortic LRV or venous collar.

FIGURE 1 Computed tomography scan of a retroaortic left renal vein.

Circumaortic LRV or venous collar (Figure 2), the most common renal vein anomaly, is seen in up to 8.7% of patients and carries the most risk for inadvertent injury. The anterior component of the renal collar can easily be mistaken for normal anatomy, whereas the retroaortic component of the renal collar is not readily visible and is easily injured during aortic dissection or clamping. The retroaortic venous components of renal vein anomalies occasionally coalesce with large lumbar and retroperitoneal veins to form a complex retroaortic venous system that is also vulnerable to injury during dissection and clamping.