Narrowed renal artery. Coloured 3D computed tomography (CT) scan of the interior of a patient's right renal artery showing stenosis (narrowing). The right renal artery branches from the aorta, the body's main artery, and serves the right kidney. The artery has become narrowed by atheroma, fatty deposits (shown by the irregular surface) that thicken the inner coating of the arteries. Treatment is either with balloon angioplasty or a stent to reopen the artery.