The causes of widening of the intercostal space may be related to diseases such as pneumothorax, pleural effusion, and chronic obstructive pulmonary disease. 1. Pneumothorax: When outside air enters the pleural cavity and accumulates, sudden chest pain will occur. At the same time, you will feel shortness of breath, fatigue and rapid heartbeat, which is prone to occur in tall, thin men. Widening of the intercostal space may occur due to increased pressure in the chest cavity caused by the accumulation of gas in the chest cavity. 2. Pleural effusion: the increase of fluid in the chest cavity can be caused by lung inflammation, tumor, pleurisy, etc. A large amount of pleural effusion will cause widening of the rib space on the affected side, which may be accompanied by fever, cough, chest pain, dyspnea, emaciation and other symptoms. 3. Chronic obstructive pulmonary disease (COPD): It is a common disease characterized by continuous airflow limitation, which develops progressively and causes irreversible lesions in the lungs. The performance of chronic cough and sputum, shortness of breath, chest tightness, dyspnea, chest anterior and posterior diameters increase, widening of the intercostal space, widening of the lower angle of the sternum under the raphe, the performance of barrel-shaped chest. There are other reasons for the widening of the intercostal space, it is recommended to go to the hospital in time, after clarifying the cause of the disease, symptomatic treatment.