Left subcostal pain may be caused by trauma, gastroduodenal diseases and costochondritis. 1. Trauma: if the patient recently suffered a strong impact on the left subcostal area, it may lead to some damage to the local soft tissues, and the damaged soft tissues may appear edema, pain, combined with the infection will also appear in the local area of redness, warmth, and fluctuating sensation. 2. Gastroduodenal diseases: such as gastritis, gastroduodenal ulcer, gastric cancer, etc., the patient’s excessive secretion of gastric acid, reflux of gastric contents to stimulate esophagus, and infiltration of gastric cancer into the surrounding tissues will lead to hidden pain and discomfort in the left side of subcostal area, and the patient will also suffer from coughing, vomiting, and loss of weight. 3. Costochondritis: mostly caused by non-infectious factors, manifested as chest pain and pressure pain, and caused by infectious factors, local skin redness, swelling, heat and pain can also occur. The pain may radiate to the back of the shoulder, armpit, cervical and thoracic, and may be aggravated by deep breathing, activity or exertion. Other conditions can also lead to the patient’s left subcostal pain, it is recommended that the patient consult a doctor in a timely manner for examination, to clarify the cause of the disease, and under the guidance of the doctor to carry out the appropriate treatment.