Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest were obtained . Slight increase in interstitial markings bilaterally consistent with interstitial edema has improved since the prior study with minimal remaining . Again patchy left base retrocardiac opacity is seen which may be due to atelectasis , though an underlying consolidation may be present . There is no pleural effusion or pneumothorax . The cardiac and mediastinal silhouettes are stable .
    OUTPUT:
    
Interval improvement in interstitial edema with mild remaining . Patchy left base retrocardiac opacity is again seen , which could be due to atelectasis or consolidation . Additionally , small patchy opacity projecting over posterior left sixth rib is new since the prior study and could represent a focus of infection .