Which anatomic landmark demarcates upper gastrointestinal bleeding from lower gastrointestinal bleeding?

The ligament of Treitz, or the peritoneal ligament, which separates the third (retroperitoneal) poion of the duodenum from the fouh (peritoneal) poion of the duodenum, traditionally demarcates upper GI bleeding from lower GI bleeding. Bleeding proximal to this landmark tends to produce melena or black tarry stools. Bleeding distal to this landmark tends to produce hematochezia or red blood per rectum.The ileocecal valve separates the terminal ileum from the cecum.The papilla of Vater is where the pancreatic duct and common bile duct empty into the duodenum.The pylorus is the sphincter separating the stomach from the duodenum.