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18. Coverage of Abdominal Aortic Grafts
The interposition of viable tissue between an aortic graft prosthesis and the posterior wall of the duodenum has long been recognized as an important technique to limit the incidence of graft-enteric erosions and fistulae. In patients with aortoiliac occlusive disease, the periaortic tissue is approximated over the aortic prosthesis to insulate the graft from the adjacent bowel.
Aneurysm Wall Wrap
In patients with aneurysmal disease, the redundant aneurysm wall is wrapped around the implanted aortic graft before approximating the periaortic tissue. The redundant aneurysmal wall is usually closed over the graft with an attempt to minimize the dead space between the aortic prosthesis and the aortic wrap. In the presence of a very large aneurysmal sac, a vest-over-pants closure of the excessively redundant aortic wall may be necessary.
Omental Flaps
Occasionally, the aneurysmal aortic wall or the periaortic tissue cannot adequately cover the aortic prosthesis, especially at the level of the proximal anastomosis. This can be encountered in patients with small aneurysms or in thin patients with aortoiliac disease where an end-to-side aortobifemoral graft has been placed. Similarly, in patients in whom an aortorenal bypass or an aortomesenteric bypass has been performed in addition to an aortic reconstruction, coverage of the bypass grafts with periaortic tissue may be hard to perform without compressing the aortorenal or aortomesenteric bypass. In these situations, omental flaps can be developed and used to cover the aortic prosthesis [1, 2, 3]. Omental flaps have also been used in the management of infected aortic grafts to wrap the transected aortic stump.
The omental flap can be based on any patent omental artery. In thin patients, the entire omentum may have to be used as a flap. To cover the aortic prosthesis, the omental flaps are placed in either an anticolic or a retrocolic position. When using the anticolic position, there is a potential for the development of an internal hernia between the omentum and the colon mesentery [2]. Securing the omentum with a running suture along its edges can be effective in closing any potential hernia defects. The retrocolic position of the omental flap can avoid the creation of a potential hernia defect. However, this method usually requires the mobilization of the omentum from the colon and then creating a defect in the mesocolon to pass the omental flap to the desired location.
A simple technique is to create a flap based on the left omental artery, which is usually a constant anatomical finding [3]. The flap is created by dividing the omentum in an avascular plane in a direction perpendicular to the transverse colon. The splenic flexure will serve as the base of the flap, which usually measures 10–15 cm in width. The graft to be covered is exposed. The flap is allowed to fold gently over the transverse colon mesentery and is placed over the aortic prosthesis. The flap is first secured in place with few interrupted 3-0 silk sutures. A running 3-0 silk suture is also used to secure the edges of the flap to the mesocolon to prevent any herniation between the transverse colon and the omentum. In this technique, the omentum is divided in only one plane. The major part of the omentum supplied by the right and middle omental arteries is left intact and can still be placed under the midline abdominal incision.
Aneurysm Wall Wrap
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