The main symptom of duodenal ulcer is pain in the upper abdomen, which can be dull, burning, swelling, severe pain, or hunger-like discomfort. Typically, the pain occurs in the fasting state, that is, when hunger occurs on an empty stomach before a meal. The pain can be relieved after eating, or by eating alkaline foods such as soda crackers. Patients often experience pain from 10:00 to 11:00 am and from 4:00 to 5:00 pm. It also occurs at night on an empty stomach, especially in the second half of the night, and often wakes up with pain. The pain is mostly burning or dull and “rhythmic”, i.e., “pain-feed-relieved”. The pain can sometimes radiate to the corresponding area of the back. It may be accompanied by acid reflux, vomiting, and gastric distention. The typical patient’s abdominal pain tends to have a seasonal pattern, occurring in the fall, winter, or winter-spring, and it is not uncommon for the pain to recur and resolve over multiple years. This is known as “cyclic” pain. It can be relieved on its own. The pain is often afraid of eating cold food and drinks, and likes heat and pressure. The pain worsens when drinking alcohol or eating uncontrollably. The pain is aggravated by stress and exertion. In some patients with duodenal ulcers, gastrointestinal bleeding occurs when the ulcer erodes the blood vessels. Ulcers are the most common cause of upper gastrointestinal bleeding in humans, and bleeding can occur with vomiting of blood, black stools, etc., requiring emergency treatment. In severe cases, perforation may occur, and sudden onset of severe abdominal pain, which is unbearable, also requires emergency treatment. Some patients present with bleeding and perforation on the first ulcer attack. A small number of patients with duodenal ulcers have no symptoms and are “silent ulcers”. These ulcers are more likely to develop complications. Therefore, although duodenal ulcers have typical symptoms, they cannot be detected by symptoms alone, and clinical diagnosis still depends on gastroscopy.