The distended feeling in the left chest is considered to be caused by chronic superficial gastritis, bacterial pneumonia, pancreatitis and intercostal muscle strain. 1. Chronic superficial gastritis: Chronic superficial gastritis may cause flatulence of the stomach, resulting in elevation of the diaphragm, accompanied by distension of the lower left lateral part of the chest, and may also be accompanied by symptoms of indigestion. 2. Bacterial pneumonia: Bacterial pneumonia is often accompanied by cough, sputum, fever, dyspnea and other symptoms, and the patient has discomfort such as tightness and pain in the left chest due to pleural friction or inflammatory stimulation. 3. Pancreatitis: Patients with pancreatitis may experience discomfort such as left chest tightness, distension and pain due to involvement pain. 4. Intercostal muscle strain: when repeated exertion or strenuous exercise can cause intercostal muscle strain, the left anterior chest soreness and swelling feeling, especially when breathing pain is obvious, intercostal pressure pain. If the feeling of swelling in the left chest does not improve through rest, it is recommended that the patient consult a regular hospital in a timely manner to clarify the cause of the disease, and then give targeted treatment or therapy.