Peptic ulcer disease refers to ulcers that can form in the lower esophagus, stomach, or duodenum. Ulcers occur when there is an imbalance between the erosive effects of gastric juice, which has a high acid content, and neutralizing factors that protect the digestive system lining. The most common causes of peptic ulcers are infection with H. pylori bacteria and chronic use of nonsteroidal anti-inflammatory drugs. Other potential causes include certain infections, drugs, toxins, diseases, and idiopathic hypersecretory states.