Diaphragmatic rupture often results from blunt abdominal trauma, which is usually associated with motor-vehicle accidents as in this case.
The rupture occurs due to increased intra-abdominal pressure from forceful impact.
An hour-glass (or collar) appearance is present due to the stomach herniating through a small defect in the diaphragm comparative to the amount of stomach either side of the diaphragm.
If left uncorrected ischemia may occur. Prompt surgical correction as in this case is necessary.