This case emphasizes the importance of assessing the hemidiaphragms on trauma chest x-rays. If the diaphragm outline cannot be clearly traced then one must look carefully for signs of diaphragm rupture such as herniated viscus in the chest and positive mass effect, both of which could be seen in this man. An intercostal catheter was presumably inserted in this case because the trauma team incorrectly thought the dense left lower zone opacity was hemothorax. It is important to remember that while hemothorax does produce positive mass effect (mediastinal shift), it should not be localized to the lower zone and should instead produce a generalized increased density throughout the hemithorax of a supine patient.