Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP and lateral views of the chest . Linear opacity at the left lung base most suggestive of atelectasis . The lungs are otherwise essentially clear . Blunting of the posterior costophrenic angle on the left may represent trace effusion . Cardiac silhouette is within normal limits noting prominent left cardiophrenic fat pad , unchanged . No acute osseous abnormality detected .
    OUTPUT:
    
No acute cardiopulmonary process . Possible trace left effusion .