Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest . There is persistent left basilar opacity compatible with an effusion . There is probable underlying atelectasis noting superimposed infection can not be excluded . Blunting of the right posterior costophrenic angle is compatible with trace right - sided effusion . The right lung and left upper lung remain clear . Prosthetic valves are again noted . Cardiomediastinal silhouette is unchanged as are the osseous and soft tissue structures noting a mid thoracic wedge deformity .
    OUTPUT:
    
Persistent left - sided pleural effusion not significantly changed with probable underlying atelectasis . Component of infection can not be excluded .