Aortic atheromas. Coloured 3D computed tomography (CT) angiogram of the abdomen of a 60-year-old patient with atheromatous plaques in the infrarenal aorta (centre), with the kidneys also visible (upper centre left and right). An atheroma is the deposition of fatty material on the inner walls of an artery. This can greatly reduce the size of the lumen (inner space), causing a reduction in blood flow (ischaemia) to the tissue supplied by the artery.