A 30-year-old man presents soon after passing black, tarry, foul-smelling stools. This is his first such episode. He has also had mild epigastric pain for one month, which was worse after meals. His bowel habits are unchanged from earlier. There is no history of recent trauma. His medical, surgical, and family histories are unremarkable; in particular, there is no history of coagulopathies. He does not smoke. He has consumed four to five units of alcohol each week for over a decade now.