Tension pneumothorax. Axial MDCT in lung window at the level of the pulmonary trunk shows increased volume of the right hemithorax due to a large pneumothorax. This finding reduces the ipsilateral pulmonary volume and shifts the mediastinum to the left. A small contusion focus in the posterior segment of the right upper lobe and subcutaneous emphysema are also seen. This is an indication for immediate chest drainage.