Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal and hilar contours are within normal limits . There is very mild pulmonary vascular congestion without pulmonary edema . A subtle patchy opacity at the base of the left lung is demonstrated in the retrocardiac area . No pleural effusion or pneumothorax is seen .
    OUTPUT:
    
Nonspecific patchy left basilar opacity , which could reflect patchy atelectasis , localized aspiration , or an early focus of pneumonia . Short - term followup radiographs may be helpful in this regard if warranted clinically . .