Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post mitral valve replacement . There is a dual - lumen venous catheter terminating at the upper aspect of the right atrium , as before . The heart is again moderately enlarged . Slightly prominent central pulmonary vascularity appears to represent a baseline finding but is slightly more prominent . A left retrocardiac opacity persists and obscures the left hemidiaphragm posteriorly . This is suspected to primarily represent pleural effusion with atelectasis , also noting slight thickening of all fissures suggesting mild fluid overload . It is difficult to completely exclude an infectious etiology , however . The bony structures are unremarkable .
    OUTPUT:
    
Findings suggesting slight pulmonary vascular congestion . Persistent small left - sided pleural effusion with patchy posterior left lower lobe opacity . Pulmonary opacification may be due to atelectasis associated with persistent effusion , but an infectious etiology is not entirely excluded by this study .