Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is normal in size . The mediastinal and hilar contours appear within normal limits . Mild blunting of the left posterior costophrenic sulcus makes it difficult to exclude a trace effusion , but a pleural effusion is doubtful . There is no pneumothorax . The lungs appear clear . Bony structures are unremarkable .
    OUTPUT:
    
No evidence of acute cardiopulmonary disease .