Pain under the left rib cage can be examined through routine examination by a specialist, X-ray film, ultrasound, and electronic gastroscopy. 1. Routine examination by specialist: Firstly, the doctor will ask about the medical history and history of trauma, and then form a preliminary diagnosis of the condition of the affected area through visual inspection, palpation, percussion and auscultation. 2. X-ray: If the pain is suspected to be caused by rib fracture, costochondritis, tuberculosis, etc., chest X-ray or CT examination can be used to make a clear diagnosis. 3. Ultrasound: Since the spleen and pancreas are located under the left side of the ribs, the pain under the left side of the ribs may also be related to internal organs such as the spleen and pancreas, which can be determined by abdominal ultrasound. 4. Electronic gastroenteroscopy: left subcostal pain can also be seen in gastric diseases such as gastric ulcer and gastric bleeding, which can be examined by electronic gastroscopy. If the left subcostal pain cannot be relieved, it is recommended to go to the hospital in time to be examined by a specialist, and then perform the necessary auxiliary tests to clarify the cause of the disease and take corresponding therapeutic measures.