Renal artery stenosis is a narrowing in the artery that supplies the kidney with blood. Therefore the kidney senses low perfusion pressure and assumes that the body has low blood pressure, and produces chemicals that raise blood pressure. The patient subsequently experiences high blood pressure or hypertension. The stenosis is usually at the origin of the renal artery and occurs predominantly in elderly patients who have atherosclerosis and vascular disease elsewhere also. They are usually on mu