The chest x-ray AP view shows a possible widened mediastinum (considering all the technical issues – AP view, rotated film, poor inspiration). The other obvious feature is  the stomach lying within the left hemithorax.

With concerns for an aortic dissection, the patient went on to have an emergent CT which revealed a gastric volvulus with ischemia of the wall of stomach and portal venous gas. The patient had a bad outcome.

CT images :

Gastric volvulus is a rare condition but to be considered as a differential in an unwell patient with a known hiatus hernia when they present with severe epigastric pain and shock.