Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a subtle opacity in the left costophrenic angle with loss of the diaphragmatic margin in that region . Otherwise no focal opacities are seen elsewhere in the lungs . There is no pleural effusion . Cardiomediastinal and hilar contours are unremarkable . No pneumothorax .
    OUTPUT:
    
Small left lower lobe consolidation may represent pneumonia versus atelectasis .