Review Question - QID 210884

A 58-year-old woman presents to her primary care physician for a fever and cough. She states that she has not felt well since yesterday and recently interacted with her grandson who has the flu. Otherwise, she only complains of spitting up undigested food when she eats solid food and has only been able to drink liquids during meals. She has a past medical history of diabetes and diverticulosis. Her temperature is 102°F (38.9°C), blood pressure is 167/98 mmHg, pulse is 100/min, respirations are 22/min, and oxygen saturation is 94% on room air. A chest radiograph is obtained as seen in Figure A. She is started on appropriate medical therapy. Which of the following is the most appropriate next step in working up this patient's underlying condition?