Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Subtle retrocardiac left lower lobe opacity may be due to overlap of vascular structures however a consolidation due to pneumonia is not excluded in the appropriate clinical setting . There may be mild vascular congestion . No pleural effusion or pneumothorax is seen . The cardiac silhouette is top - normal . Mediastinal contours are unremarkable .
    OUTPUT:
    
Subtle retrocardiac left lower lobe opacity may be due to overlap of vascular structures however a consolidation due to pneumonia is not excluded in the appropriate clinical setting .