Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Renal Artery Stenosis ?
    ### Response:
    About 90 percent of RAS is caused by atherosclerosisclogging, narrowing, and hardening of the renal arteries.2 In these cases, RAS develops when plaquea sticky substance made up of fat, cholesterol, calcium, and other material found in the bloodbuilds up on the inner wall of one or both renal arteries.
    