The inferior mesenteric artery is clamped (Figure 6). The aortic side may be divided and ligated from without or, conversely, oversewn from within after the aneurysm is opened. Usually, this vessel is small and sclerotic, in which case its sacrifice is of little consequence. In some instances, it is large and serves as a major contributor to the left colon blood supply, especially if internal iliac and mesenteric occlusive disease is present. In such cases the vessel will be patent but will not exhibit back bleeding. Reimplantation of this vessel into the aortic graft may be required to protect the colon.
The common iliac arteries then are exposed on their anterior, lateral, and medial surfaces in preparation for clamp placement. It is not necessary to encircle these vessels completely, and dissection posteriorly can result in troublesome hemorrhage from the underlying iliac veins. During the iliac artery exposure the ureters are identified and protected from injury throughout the procedure (Figure 6).
In the past, certain grafts required preclotting; however, this is not necessary with woven grafts, knitted grafts sealed with collagen or gelatin, or expanded polytetrafluoroethylene grafts.
Heparin is then injected systemically or directly into the aneurysm to provide protective anticoagulation for the extremities during aortic clamping.
Angled vascular clamps are applied to the distal common iliac arteries. An aortic clamp is used to occlude the aorta proximal to the aneurysm and distal to the renal arteries. A careful identification of the position of the renal arteries is mandatory before clamp application. The aneurysm is then opened through a linear arteriotomy (Figure 7). The mural thrombus is extracted (Figure 8). Bleeding from the paired lumbar arteries is controlled with full-thickness mattress or figure-of-eight nonabsorbable suture ligatures (Figure 9). The aortic cuff is next prepared by dividing all but the posterior wall. Leaving this portion attached prevents troublesome bleeding from lumbar veins often found in this area (Figure 10). The iliac arteries are prepared in similar fashion; the posterior wall is undisturbed to protect the iliac veins (Figure 10). Alternatively, some surgeons prefer to completely transect the proximal aorta and the distal iliac arteries so as to provide free circumferential cuffs for graft anastomoses.