Hiatus hernia, coloured X-ray. Side view of a patient suffering from a hiatus hernia, the protrusion of the stomach through the diaphragm into the chest. The spine (blue, down left) and ribs (blue, upper right) are also seen. A hiatus hernia occurs when part of the stomach protrudes into the chest cavity through the hole through that the oesophagus (gullet, top left) normally passes. The most usual symptom is gastro- oesophageal reflux, the passage of gastric juice up the oesophagus.