A 70 yo presents to your ED intubated by medics. The patient was reportedly having worsening respiratory distress, was trialed on CPAP but failed, ultimately requiring intubation prior to ED arrival. A stat portable CXR is done and shown below. What's the diagnosis?  (scroll down for answer)

Answer: Complete opacification of R hemithorax

• Differential for complete "white out" of a hemithrorax is most commonly:
• Pleural effusion (fluid, blood, empyema)
• Atelectasis (from mucus plug, obstructive mass, mainstem intubation)
• To differentiate- look at the mediastinum for the answer! (is the trachea central or deviated toward/away from the opacified side?)
• Trachea deviates toward opacified side:
• pneumonectomy
• total lung collapse  (mainstem intubation)
• pulmonary hypoplasia 
• Trachea midline:
• consolidation
• pulmonary edema/ARDS
• Trachea deviates away from opacified side: 
• pleural effusion
• large pulmonary mass
• Can also use POCUS to to look for a large effusion if unclear/to confirm CXR !

References: 

Corne J, Carroll M, and Delany D. Chest X-ray Made Easy. 2nd ed., Churchill Livingstone, 2002