Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable upright AP view of the chest was obtained . Limited study due to patient positioning and low lung volumes . The patient 's chin obscures the left upper lung region . Patchy and linear opacities in both lung bases are most likely due to subsegmental basilar atelectasis . Moderate cardiomegaly . Evaluation of the mediastinal contours is limited due to patient rotation . Possible trace left pleural effusion . The extreme left costophrenic angle is not imaged . There is no free air below the right hemidiaphragm . ___ rods are located in the spine .
    OUTPUT:
    
Limited study . Probable bilateral basilar atelectasis .