Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patchy left base opacity raises concern for atelectasis and overlapping vascular structures , but pneumonia is not excluded in the appropriate clinical setting . Slight blunting of the posterior costophrenic angles is chronic . No large pleural effusion is seen . There is no pneumothorax . The lungs remain hyperinflated , suggesting chronic obstructive pulmonary disease . The cardiac and mediastinal silhouettes are stable . There is no pulmonary edema .
    OUTPUT:
    
Patchy left base opacity may be due to combination of atelectasis and overlying vascular structures but pneumonia is not excluded in the appropriate clinical setting .