Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: New retrocardiac left lower lobe collapse may be due to mucous plugging or aspiration . Small left pleural effusion . Opacity in the left mid lung likely pneumonia . No pulmonary vascular congestion . There is no pneumothorax . Cardiac size is normal . Hilar contours are unchanged .
    OUTPUT:
    
New left lower lobe collapse .