mrcem2-0739

A 60 year old comes to the emergency department with worries of feeling nauseated and vomiting blood. The patient shows you a tissue paper with mostly coffee ground vomit and a few specks of fresh red blood. The patient mentions experiencing on-and-off abdominal pain for a few weeks. You suspect that the patient is experiencing an upper gastrointestinal bleed. What is the primary cause of upper gastrointestinal bleeding in adults?