Left subcostal pain is associated with local tissue abnormalities, which may be caused by chondromalacia, intercostal neuralgia, pulmonary diseases, stomach diseases, etc. 1. Costochondritis: Trauma, infection, or abnormal immune system may trigger costochondritis, which may cause pain due to irritation of the surrounding tissues. 2. Intercostal neuralgia: it is closely related to nerve damage, and the corresponding pain will radiate to the surrounding area. 3. Intra-pulmonary diseases: Pneumonia, pleurisy, tumors in the lungs, which cause stimulation to the surrounding tissues, may trigger the corresponding symptoms. 4. Stomach diseases: gastritis, gastric cancer, etc. may cause irritation to the neighboring tissues, which may also cause pain and discomfort in the corresponding areas. If you have vague pain under the left rib cage and the symptoms continue to worsen, you need to be admitted to the hospital in time for observation, and after checking the specific physical condition, you should carry out standardized treatment under the guidance of the clinician, so as to avoid delaying the condition.