The Inferior Vena Cava After Ligation and Plication

The first well documented case of occlusion of the inferior vena cava was reported by Morgagni in 1769 (8). Routes of collateral return of the obstructed cava were studied by Sappey and Dumontpallier (11). Using injection and dissection technics, they were able to visualize superficial and deep veins of the abdominal wall and lateral thorax, the lumbar, the azygos, the portal, and the vertebral plexus of veins. It was not until 1935, however, after venography studies of the cava were described by Dos Santos, that roentgenography began to play a significant role in the study of collateral channels. While venographic studies of the occluded inferior vena cava are not new (4, 14), it is only recently that attention has been focused on the collateral channels after a ligation, plication, filter, clipping, or interruption procedure on the inferior vena cava (1, 3, 6, 7, 10, 13, 15). The chief purpose of this report is to examine in detail the primary and alternate routes of venous return after ligation or plication. The incidence of thrombi below or above the procedure, recurrent embolization, venous pressure measurements, and their significance have also been studied. Anatomy Anatomical Routes of Venous Return After Occlusion of Inferior Vena Cava The routes available for return of blood from the pelvis and lower extremities after occlusion of the inferior vena cava are numerous. For the sake of descriptive convenience, we have divided them into four groups: 1. Central Channels: The central channels (Fig. 1) are composed of the ascending lumbar, internal and external vertebral venous plexus, hemiazygos-azygos system, and the cava above the level of occlusion. The ascending lumbar veins are usually valveless and lie deep to the psoas muscle adjacent and parallel to the lumbar spine (2). They freely and regularly communicate with the inferior vena cava via the caval portion of the lumbar vein and with the internal vertebral venous plexus via the intervertebral veins (Fig. 2). The azygos arises from the dorsal aspect of the inferior vena cava at the level of the second lumbar vertebra (12). The hemiazygos originates from the renal vein via the renal azygos lumbar plexus. Both pass through the crura of the diaphragm and continue upward into the thorax. Subcentral anastomoses between the two exist at the twelfth dorsal vertebra and again at the level of the azygos-superior vena cava junction. The vertebral venous network is an intricate one, situated outside the thoracoabdominal cavity (Fig. 2). Its valveless anastomosis allows blood delivery from or to the cavity system of veins. Valves are absent in the epidural component but are present intradurally. The external plexus anteriorly and posteriorly communicates with the ascending lumbar and the internal vertebral venous plexus (Fig. 2). Batson (2), using animals and the human cadaver, demonstrated free communication of the vertebral venous plexus with cranial venous sinuses.