A 68-year-old man presents to the emergency department with severe abdominal pain, headache, chest pain, and shortness of breath for the past three days. He has a history of coronary artery disease, asthma, and hypertension diagnosed three months ago, which has been resistant to hydrochlorothiazide and lisinopril. Over the last month, his GFR has rapidly declined. On examination, his blood pressure is 210/115 mmHg, and he has diffuse pulmonary crackles bilaterally. An abdominal bruit is noted on the left side. A chest X-ray shows bilateral fluffy pulmonary infiltrates. Renal artery stenosis is suspected. What is the most likely cause of renal artery stenosis in this patient?
