An 84-year-old man with a lengthy history of smoking survived a small myocardial infarction 2 years ago. He now reports chest and leg pain during exercise. On physical examination, his vital signs are temperature, 37.1deg C; pulse, 81/min; respirations, 15/min; and blood pressure, 165/100 mm Hg. Peripheral pulses are poor in the lower extremities. There is a 7-cm pulsating mass in the midline of the lower abdomen. Laboratory studies include two fasting serum glucose measurements of 170 mg/dL and 200 mg/dL. Which of the following vascular lesions is most likely to be present in this patient?

Abdominal aneurysms are most often related to underlying aortic atherosclerosis. This patient has multiple risk factors for atherosclerosis, including diabetes mellitus, hypertension, and smoking. When the aneurysm reaches this size, there is a significant risk of rupture. An aortic dissection is typically a sudden, life-threatening event with dissection of blood out of the ascending aortic lumen, typically into the chest, without a pulsatile abdominal mass. The risk factors for atherosclerosis and hypertension also underlie aortic dissection. An arteriovenous fistula can produce an audible bruit on auscultation. Classic polyarteritis nodosa (PAN) can produce small microaneurysms in small arteries, most often renal and mesenteric. Takayasu arteritis typically involves the aortic arch and branches in children. Thromboangiitis obliterans (Buerger disease) is a rare condition in which muscular arteries become occluded in the lower extremities in smokers.