One of the rare, yet major complications that can occur during rectal dissection is presacral bleeding. This injury can result in massive blood loss, hemodynamic instability, and even death.
An anatomical study was carried out across 100 pieces of sacrum to study the anatomy of the presacral venous plexus. They found that in 16% of the specimens, there were one to several large foramina, which are the sites for the basivertebral veins to penetrate. In other specimens, these foramina were very small. These are located at the level of S3–S5.1 The adventitia of these presacral veins is attached to the sacral periosteum at the openings of these foramina. This explains why these veins can be injured during blunt dissection of the rectum, where the surgeon retracts the rectum anteriorly and bluntly dissects through the posterior plane, and will pull on the presacral fascia and injure these delicate veins near their foramina. These veins, consequently, will retract inside the bone, and will cause massive bleeding.
The presacral venous plexus is located anterior to the sacrum, and it is formed by two lateral presacral veins, and the middle sacral vein. These are interconnected by communicating veins. The presacral venous plexus is connected to the internal vertebral venous system through the basivertebral veins that pass through the sacral foramina.
Wang et al.1 classified the patterns of presacral vein injury to three different types: (1) bleeding from injury to the presacral venous plexus, (2) bleeding from the pelvic surface of the distal sacrum, and (3) bleeding from an injury to a large caliber sacral basivertebral vein (Figure 15-1).
Three types of presacral vein injury.
The amount of bleeding depends on the size of the vessel injured, and the hydrostatic pressure in the sacral venous plexus. The lithotomy position can increase the hydrostatic pressure up to double or triple the pressure in the inferior vena cava, and thus lead to more profuse bleeding.1 In addition, due to the lack of valves in this complex venous network, this will make the bleeding even worse.
RISK FACTORS AND MECHANISM OF INJURY
Risk factors that might lead to this injury could be related to anatomical factors or technical factors. Anatomical factors are those such as a very narrow pelvis or severe fibrosis in the dissection planes posteriorly secondary to the radiation effects leading to fixation of the posterior rectum to the anterior surface of the sacrum.2 Additional risk factors include recurrent rectal cancer, or extension of the tumor posteriorly. There are few intraoperative technical errors that lead to this injury.
The surgeon may be in the wrong plane where the dissection is too posterior.
Blunt dissection in ...