Gastric and duodenal ulcers and acid reflux, cutaway illustration. The ulcers are on the internal stomach (centre) and intestine (centre left) lining, with the latter in the duodenum, the first part of the small intestine where food exits the stomach. The oesophagus (upper centre) is a tube that brings food from the mouth to the stomach. An ulcer is formed by the loss of inflamed and dying tissue. Stomach acid, alcohol and aspirin can all make the condition worse. Antibiotics are used if Helicobacter pylori bacteria are thought to be responsible. The differences between chronic and acute gastritis are labelled here, as are the features of acid reflex: a stricture in the oesophagus, and reflux oesophagitis.