If the aorta is severely diseased or occluded, or both iliac arteries are occluded, then a complete bypass taking blood from the aorta into the top of the legs can be carried out (an aorto bifemoral graft: see Figure 6.7). A synthetic trouser (shaped like a pair of trousers) graft is used. This is sewn directly into the aorta, then carried down into the top of the legs, where it is joined to the femoral arteries. Although this is a major procedure, the operation is extremely effective. The death rate of this procedure should be less than 1%, particularly when patients with serious heart problems have been excluded. The major complications that can arise include infection, blockage of the graft and blockage of small vessels supplying the bowel and the spinal cord. Blockage of the vessels supplying the bowel is usually recognised at the time of surgery and appropriate steps are taken. Blocking of the vessels supplying the spinal cord is unpredictable. Although this is an extremely rare complication, the results are devastating.