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 acidic digestive juices which are secreted by the stomach cells.