Illustration of the digestive organs of the body. At front is the stomach, behind it is the pancreas (yellow), and the small (pink) and large (brown) intestines. There are two ulcers on the inner lining of the stomach. Gastric ulcers generally cause a dull pain after a meal. They can be caused by stress, but in most cases infection with the bacterium Helicobacter pylori is responsible. In some cases gastric ulcers develop when the stomach lining is inflamed over a long period.