Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A large , left unilateral pleural effusion and left lower lobe collapse are present without appreciable mediastinal shift . A linear streak of atelectasis or scarring is noted in the right mid lung . Both apices are clear . There is no pneumothorax . No distracted bony fracture is identified .
    OUTPUT:
    
Large unilateral left pleural effusion appears to be chronic due to lack of mediastinal shift . Comparison to prior chest examinations would be helpful . Consideration should be given to hemothorax if there is a positive trauma history with other possibilities including infection or malignancy .