Physiological analysis of pelvic and epidural plexus veins in rabbits

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Excessive bleeding is a significant problem during total sacrectomy. Ligation of the internal iliac veins to control bleeding from the pelvic venous plexus has been reported to be mandatory. However, despite ligation of the internal iliac veins, excessive hemorrhage from the pelvic and epidural venous plexuses is often encountered. We postulated that ligation of the internal iliac veins increases blood loss during total sacrectomy and we investigated the influence of ligation of the internal iliac veins on the pelvic and epidural venous plexuses in white rabbits. We also investigated the influence of the animal's operative position on the epidural venous pressure. Venography was performed to study the differences in blood flow patterns before and after ligation of the internal iliac veins. Without ligation, contrast medium passed into the inferior vena cava, but not into the epidural venous plexus. The epidural venous plexus was contrast-filled when the internal iliac veins were ligated. The pressure in the internal iliac veins was increased with their ligation, and decreased with ligation of the abdominal aorta. The pressure was also decreased with intentional bleeding from the epidural venous plexus, and with changing the animal's position to headdown. Ligation of the internal iliac veins leads to congestion of the pelvic venous and epidural venous plexuses. Ligation of the internal iliac arteries and positioning the animal headdown were effective ways to resolve the congestion in these venous plexuses.