Review Question - QID 215013

A 67-year-old man presents to the emergency department with abdominal pain and diarrhea. These symptoms have been going on for the past month and have been gradually worsening. He has both abdominal pain and very dark diarrhea after eating large meals. The patient has a history of coronary artery disease, peripheral vascular disease, and type 2 diabetes mellitus. His medications include atorvastatin, lisinopril, aspirin, metformin, and cilostazol. However, he is poorly compliant with his medications. He drinks approximately 10 standard alcoholic drinks per week and has smoked 1 pack of cigarettes per day for the past 45 years. His temperature is 98.7° F (37.0°C), blood pressure is 158/93 mmHg, pulse is 91/min, and respirations are 13/min. Physical exam reveals an obese, nontender abdomen with no rebound or guarding. The patient has smooth, hairless lower extremities. He states he is currently pain-free. Which of the following is the most appropriate diagnostic test for this patient?