nid:1512662839571 states the same card but says ampulla of Vater. Neither have UW tags. For what it’s worth, de Virgilio says “bilious emesis implies a patent pylorus with obstruction distal to the ampulla of Vater.” in a section on distinguishing non-bilious vs. bilious vomiting (p. 407, 2e). So my vote is ampulla of Vater.
My understanding was that the ligament of Treitz is commonly used to classify GI bleeds into upper (proximal to LOT) and lower (distal to LOT).