Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest . Linear opacity at the left lung base most suggestive of atelectasis . The lungs are otherwise clear without consolidation or large effusion . There is , however , blunting of the posterior costophrenic angles , raising possibility of trace effusions . Cardiomediastinal silhouette is within normal limits . Descending thoracic aorta is again noted . No acute osseous abnormality is identified .
    OUTPUT:
    
Small pleural effusions , new since prior . Otherwise , no change from prior .