Peptic ulcer: An ulcer in the lining of the stomach, duodenum, or esophagus. Peptic ulcers affect millions of people in the US yearly. Ulcer formation is related to Helicobacter pylori bacteria in the stomach, use of anti-inflammatory medications, and cigarette smoking. Peptic ulcer pain may not correlate with the presence or severity of ulceration. Complications of peptic ulcers include bleeding, perforation, and blockage of the stomach (gastric obstruction). Diagnosis is made via barium X-ray or endoscopy. Treatment involves use of antibiotics to eradicate H. pylori, elimination of risk factors, and prevention of complications.