• Gastric or duodenal peptic ulcer
• Oesophageal or gastric varices
• Erosive oesophagitis, gastritis or duodenitis
• No lesion identified (10–15% cases; usually because the lesion is obscured by blood, difficult to identify, such as Dieulafoy's lesion, or healed by the time of the gastroscopy)

Less common or rare

• Portal hypertensive gastropathy
• Angiodysplasia
• Gastric antral vascular ectasia (GAVE), (long red stripes arising from the pylorus, also known as ‘watermelon’ stomach)
• Mass lesions (polyp or cancer)

Mallory-Weiss syndrome (see Chapter75)

• Dieulafoy's lesion (an abnormally large submucosal vessel that erodes the gastric epithelium bleeding intermittently; there is no primary ulcer and so in the absence of bleeding it is difficult to see)
• Haemobilia (bleeding from the bile duct)
• Haemosuccus pancreaticus (bleeding from the pancreatic duct)
• Aorto-enteric fistula (fistula between aneurysmal aorta or aortic graft and the gut, most often duodenum; endoscopy is primarily to exclude bleeding from other causes; the fistula may not be visualized)
• Cameron lesions (linear ulcers within the sac of a hiatus hernia at the diaphragmatic impression)