Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A portable single view chest x-ray shows mild hyperinflation with flattening of the hemidiaphragm , likely due to COPD . Heterogeneous opacity at the right lung base might be due to atelectasis . Right base pleural effusion is chronic and unchanged since ___ . Cardiomediastinal silhouette is normal and unchanged since the prior chest x-ray . No pneumothorax . Large air colon distension .
    OUTPUT:
    
Chronic right base pleural effusion with right basilar opacity compatible with atelectasis . Air colon distention .