Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal silhouette is normal . There is no pleural effusion or pneumothorax . Lung volumes are lower than on prior chest radiographs . There is increased opacity in the retrocardiac region on lateral view , likely corresponding to a region of linear opacity in the left lower lobe . There is no acute osseous abnormality .
    OUTPUT:
    
Subtle increased opacity anterior medial segment left lower lobe , which could potentially represent an early focus of pneumonia in the appropriate clinical setting .