Peptic ulcer disease (PUD) involves the development of open sores in the lining of the stomach, upper small intestine, or esophagus. It is often caused by Helicobacter pylori infection or long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs). Symptoms include abdominal pain, bloating, and indigestion. Treatment involves antibiotics, proton pump inhibitors, and lifestyle modifications.