Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a large left - sided pleural effusion without mediastinal shift consistent with compensatory atelectasis and substantial collapse of the left lower lobe . The right lung fields , hemidiaphragm , cardiac border and mediastinal silhouette are normal . Single lead pacemaker in left chest wall is unchanged .
    OUTPUT:
    
Large left - sided pleural effusion with compensatory atelectasis indicating substantial collapse of the left lower lobe .