Duodenal ulcer. Endoscope view of a large peptic ulcer (white) in the duodenum. The duodenum is the uppermost part of the small intestine. A major causative factor of peptic ulcers (up to 90 per cent of duodenal ulcers) is chronic inflammation due to the bacterium Helicobacter pylori, which can be treated with antibiotics. Another cause is the use of non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin. Healing is promoted by drugs that block the secretion of gastric acid.