This 23-year-old man was involved in a motor vehicle accident. What is the diagnosis?

Answer D. PneumothoraxThe presence of a deep, lucent, right costophrenic angle on supine chest radiography is an indirect sign of a pneumothorax. In addition, a pneumothorax with associated rib fractures and subcutaneous emphysema is evident in the right chest. The patient's endotracheal tube needs to be withdrawn further into the trachea.