Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a retrocardiac opacity concerning compatible with hiatal hernia . There is unchanged prominent interstitial marking compatible with known interstitial disease and scarring . Opacity projecting over the anterior right first rib is compatible with tortuous vessel . The cardiomediastinal silhouette and hilar contours are stable . There is likely a small right pleural effusion . No pneumothorax is seen .
    OUTPUT:
    
Small right pleural effusion . Background interstitial disease , unchanged since prior study .