The pain under the left chest is like forked air, consider the possibility of the following diseases: 1, acute pneumothorax, which can appear suddenly without triggering factors or when moving heavy objects, in addition to chest pain, there can also be dyspnea, chest X-ray can help diagnose. 2, pleurisy, with or without fever, cough, deep inspiration when the chest penetration significantly aggravated, do lung CT examination can be found near the pleura at the inflammation and a small amount of 3, angina pectoris, the pain is mostly paroxysmal, accompanied by discomfort in the back of the shoulder, and the ECG mostly shows ischemic-like changes during the attack. 4, colonic splenomegaly syndrome, mostly occurs after eating or meals, and can be relieved after massage, exhaustion or defecation.