Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright portable chest radiograph obtained . Lungs are clear . Heart size is within normal limits . Mediastinal contour is unremarkable . No large pneumothorax or pleural effusion seen . Bony structures appear intact with mild arthropathy at the AC joints bilaterally .
    OUTPUT:
    
No acute intrathoracic process .