The chest radiograph (CXR) is often the first radiologic study obtained in the evaluation of dyspnea. In the intensive care unit (ICU), portable chest radiographs are frequently ordered “STAT” to evaluate patients with new or acute onset of shortness of breath. Occasionally, there is diffuse opacification or “white-out” of a hemithorax. Though the complete differential diagnosis for “white-out” is quite large, the complete opacification of a hemithorax with no visible lung markings is usually caused by one of two main processes: atelectasis/lung collapse or massive pleural effusion, with the main types of fluids in the pleural space being serous fluid (hydrothorax), blood (hemothorax), lipid (chylothorax), and pus (pyothorax or empyema). Less common causes of white-out include a consolidative process with filling of the air spaces, such as bacterial pneumonia, soft tissue tumor, or post-pneumonectomy with the residual space filling with fluid and fibrotic material.