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.