Coloured 3D computed tomography (CT) angiogram scan of the torso of a 62 year old male patient with a dissection of the ascending aorta. This is a tear in the inner lining of the aorta (orange, down centre), the body's main artery. Blood enters the tear and separates the walls of the aorta, which can lead to a life-threatening rupture of the artery. The patient has previously had a right aortoiliac bypass, where blood flow is redirected through an artificial blood vessel (graft, orange, centre to bottom centre) to the iliac arteries of the pelvis to avoid a blockage. The dissection is preventing the blood from flowing through the graft.