Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP view of the chest . There is asymmetric left basilar opacity . Given lower lung volumes this could be due to atelectasis . Elsewhere , the lungs are grossly unchanged . Cardiomediastinal silhouette has not definitely changed although exact evaluation is difficult given rotation . Posterior spinal fixation hardware seen in the lower thoracic spine . Ventriculoperitoneal shunt catheter projects over the right anterior chest wall .
    OUTPUT:
    
Left basilar opacity potentially atelectasis given low ___ ___ ng volumes however infection can not be excluded .