A duodenal ulcer is a sore that forms on the lining of the duodenum, which is the first part of the small intestine. These ulcers can cause pain, especially when the stomach is empty, and may lead to complications if not treated. Common causes include infection with Helicobacter pylori bacteria and the use of nonsteroidal anti-inflammatory drugs (NSAIDs). Symptoms of duodenal ulcers may include burning stomach pain, bloating, and nausea. Treatment often involves medications to reduce stomach acid and antibiotics to eliminate H. pylori infection. Lifestyle changes, such as avoiding spicy foods and reducing stress, can also help manage symptoms.