What is renal artery stenosis? Renal artery stenosis (RAS, sometimes also called renal artery disease or kidney stenosis) occurs when the two main vessels that deliver blood to the kidneys become stiff or narrowed due to vascular disease. RAS is a type of atherosclerosis or hardening of the arteries, which occurs when fatty cholesterol plaques build up inside artery walls. The kidneys perform several key functions in the body, including regulating blood pressure and removing waste and toxins from the blood. Renal artery disease can reduce the amount of blood that’s able to flow into the kidneys, which can raise blood pressure and allow toxins to build up in the body’s tissues. Anyone can develop RAS, but the risk increases with age. The risk factors for any kind of atherosclerosis also apply to RAS, which means anyone with high cholesterol, hypertension, insulin resistance, or a family history of cardiovascular disease may be at higher risk for renal artery stenosis. Other medical conditions, most notably fibromuscular dysplasia (FMD), can also cause renal artery stenosis. FMD is a rare condition that affects more women than men between the ages of 25 and 50. Renal artery stenosis may not produce symptoms until it reaches a severe stage. When RAS becomes symptomatic, it often results in decreased kidney function, such as changes in urination or swelling of the feet and legs. RAS also can cause high blood pressure. Because the symptoms of RAS mimic those of other cardiovascular diseases, renal artery stenosis diagnosis often occurs during an investigation into a related condition like unexplained hypertension. As a type of atherosclerosis, renal artery stenosis may be preventable by following a heart-healthy lifestyle. Left untreated, renal stenosis can cause kidney damage or kidney failure that requires dialysis or an organ transplant. Usually, the effects of RAS develop over a long period of time and do not require emergency medical treatment.