Review Question - QID 214436

A 32-year-old man presents to the clinic with complaints of chronic chest pain for the past several years. The patient has not sought medical attention for this issue as he immigrated from Brazil and only received health insurance recently. The patient describes a dull, burning pain behind the sternum that is especially worse when he lays down and after food ingestion. The pain is responsive to over-the-counter antiacids but has been getting worse recently. He endorses a 3-lb. weight loss that the patient attributes to his symptoms, dysphagia, and cough. A physical examination is unremarkable. A subsequent barium swallow study is shown in Figure A. What is the most appropriate test that can diagnose this patient’s condition?