A stomach or gastric ulcer is a break in the tissue lining the stomach. The term 'peptic ulcer' refers to those that occur in either the stomach or the first part of the small intestine that leads out of the stomach, called the duodenum.
It was once commonly thought that stress, smoking and diet were the principal causes of stomach ulcers. However, the Helicobacter pylori (H. pylori) bacterium is now known to be responsible for most duodenal ulcers and 60 per cent of stomach ulcers. The H. pylori bacterium also prompts many symptoms of dyspepsia, or indigestion.