Also called renal artery stenosis, renal artery disease occurs when the artery that supplies blood to the kidneys is narrowed or blocked, most commonly by atherosclerosis. Atherosclerotic renal artery stenosis is usually seen in older individuals who may have vascular disease in other areas as well (such as the heart or legs). It may also be caused by medial fibroplasia, also called fibromuscular dysplasia, which occurs with abnormal development of the artery wall. Renal artery disease can cause hypertension, though it is a much less common cause than primary (no underlying cause) hypertension, and treating it can improve or even cure the hypertension. In other cases, renal artery stenosis may cause poor kidney function and correcting the narrowing may improve kidney function.