A peptic ulcer is a sore that develops on the lining of the stomach, the upper part of the small intestine, or the esophagus. Ulcers occur when the thick layer of mucus that protects your stomach from digestive juices is reduced, allowing the digestive acids to eat away at the tissues that line the stomach or small intestine.

Peptic ulcers are classified based on their location: gastric ulcers, which are ulcers that develop inside the stomach; and duodenal ulcers, which occur on the inside of the upper portion of the small intestine (duodenum). Esophageal ulcers and Jejunal ulcers can also occur when under unusual circumstances, other parts of the gastrointestinal tract are affected.