The presacral venous plexus results from anastomoses between the lateral and median sacral veins, and courses into the pelvic fascia covering the anterior aspect of the body of the sacrum. The presacral venous plexus is not directly visible during rectal surgery, and injuries to this plexus may be life-threatening. Dissection of the retrorectal plane or anchoring of the rectum to the sacral promontory as in rectal prolapse surgery exposes the patient to the risk of injury to the presacral venous plexus. The aim of this study was to identify some avascular areas in the anterior aspect of the sacrum in order to lower the occurrence of such injuries during rectal surgery. The pelvis of 10 fresh cadavers was dissected after injection of a colored resin into the inferior vena cava, and the presacral venous plexus was studied. Four avascular tetragonal areas were common to all the specimens. The corners of a square with a side of 3 cm, centered on the anterior aspect of the body of sacrum, were always contained in the avascular areas. The upper side of this square was parallel to a line passing through the sacral promontory, at a 3 cm distance from it. Staples or sutures should be placed in the avascular areas to avoid injuries to the presacral venous plexus.