Lung borders are poorly defined, even when lung X-rays or CTs are performed, which show poorly defined and relatively blurred boundaries at the edges of the lungs above. Performing an X-ray or CT examination with unclear lung borders is usually caused by factors such as lung infection and pulmonary embolism. In addition to this, infectious lesions occurring in the lungs such as pleural effusion may also be indicated above when lung radiographs are performed. If the imaging changes are caused by inflammatory infections can be effectively improved by aggressive treatment of the lungs to clear the infected foci. If the lungs are combined with acute pulmonary embolism, the examination will also find unclear lung borders, through effective treatment, the lung borders can be gradually clear. To summarize, unclear lung borders are mostly caused by pathological factors, and it is recommended to go to the thoracic surgery department of the hospital and combine with the doctor’s advice for treatment.