Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lung volumes are low . There is evidence of left lower lobe atelectasis and a small pleural effusion seen in the posterior costophrenic angle on the lateral view . The cardiomediastinal silhouette and hilar contours are normal . There is no evidence of pneumothorax .
    OUTPUT:
    
Left lower lobe atelectasis and a small posterior pleural effusion . If hypoxemia persists , pulmonary embolism should be considered as a possible etiology .