Solution: This case is an example of how prior films and multi-planar reconstructions can help you make the diagnosis. The CXR two days prior was completely normal, but the new abdominal radiographs show a space occupying process in the left posterior pleural space that has an air-fluid level. The differential based upon the plain films would be an empyema vs. a diaphragmatic hernia, with an empyema less likely since she is not at risk for that and it developed rapidly. The CT confirms that the fundus of the stomach has herniated through the diaphragm and since there is no contrast in the fundus, this suggests that the orifice is relatively tight. This was confirmed at surgery.