Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are relatively low . Left chest wall single lead pacing device obscures visualization of the left lung base . Overall , the appearance of the lungs demonstrates interval improvement . There is persistent abnormal interstitial opacity which suggests mild edema . More dense opacity in the retrocardiac region is again seen . Cardiomediastinal silhouette is stable .
    OUTPUT:
    
Slight interval improvement from previous exam from ___ of bilateral interstitial opacities suggesting pulmonary edema . Retrocardiac opacity could be any combination of effusion , atelectasis and / or infection .