Aortic bypass. Magnetic resonance angiography (MRA) scan of the abdomen of a patient who has had an aortic and iliac bypass (purple). This surgery was carried out to treat an aneurysm (bulging, weakened blood vessels) of the aorta and iliac arteries. The affected blood vessels have been replaced with a prosthesis which joins the aorta (white, top) and iliac arteries (white, lower right and lower left). The patient's kidneys are seen at upper right and upper left. MRA is a type of magnetic resonance imagery (MRI) which can show blood vessels without the need to inject the patient with a dye or tracer.