hole in the lining of the stomach, duodenum, or esophagus. A peptic ulcer of the stomach is called a gastric ulcer, an ulcer of the duodenum is called a duodenal ulcer, and a peptic ulcer of the esophagus is called an esophageal ulcer. A peptic ulcer occurs when the lining of these organs is corroded by the acidic digestive juices which are secreted by the stomach cells.