Review Question - QID 212406

A 57-year-old man presents to the emergency department after an episode of syncope. He states that he was at home when he suddenly felt weak and experienced back pain that has been persistent. He states that he vomited forcefully several times after the episode. The patient has a past medical history of diabetes, hypertension, dyslipidemia, and depression. He smokes 1.5 packs of cigarettes per day and drinks 10 alcoholic beverages each night. His temperature is 97.5°F (36.4°C), blood pressure is 97/48 mmHg, pulse is 150/min, respirations are 19/min, and oxygen saturation is 99% on room air. A chest radiograph is within normal limits. Physical exam is notable for diffuse abdominal tenderness and a man resting in an antalgic position. Urinalysis is currently pending but reveals a concentrated urine sample. Which of the following is the most likely diagnosis?