NBME practice questions and Answers latest 2023

A 67-year-old woman is hospitalized because of abdominal pain and persistent copious vomiting for 24 hours. Two weeks ago, she was hospitalized for treatment of atrial fibrillation; after cardioversion to a normal sinus rhythm, she began treatment with warfarin. Yesterday, at a follow-up visit, her INR was 6 (?? normal), and her medication was discontinued. She takes no other medications. Her temperature is 37°C (98.6°F), pulse is 120/min and regular, respirations are 20/min, and blood pressure is 100/78 mm Hg. The abdomen is distended and moderately tender; there is voluntary guarding in the epigastrium (??? source of pain) There are no masses, organomegaly, or obvious hernias. Rectal examination shows no abnormalities. Test of the stool for occult blood is negative. Her hemoglobin concentration has decreased from 13 g/dL yesterday to 7.8 g/dL today. An ECG shows a normal sinus rhythm. Which of the following is the most likely explanation for this patient's abdominal symptoms?