Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiographs demonstrate unchanged mild cardiomegaly and upper zone vascular redistribution , without frank edema . Lungs are moderately well aerated . A left retrocardiac opacity could represent an early pneumonia or sequela of aspiration . No pleural or pericardial effusion is identified . The visualized upper abdomen is unremarkable .
    OUTPUT:
    
A left retrocardiac opacity could represent an early pneumonia or sequela of aspiration . Short - term followup chest radiograph to document resolution is recommended .