Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal silhouette and hilar contours are unremarkable . Diffusely increased interstitial marking particularly at the right lung base are unchanged since ___ , but progressed slightly since ___ . Lungs are otherwise clear . Pleural surfaces are clear without effusion or pneumothorax .
    OUTPUT:
    
Subtle but diffusely increased interstitial markings particularly at the right lung base appearing largely similar to ___ of unclear etiology but possibly reflecting a component of heart failure .