Hiatus hernia: double-contrast barium meal (X-ray) of a person suffering from a hiatus hernia, the protrusion of part of the stomach through the diaphragm into the chest cavity. All or part of the stomach may extend through the opening (hiatus) that normally admits the oesophagus. Here, about 2/3rds of the body of the stomach is displaced through the hiatus. Contrast material (yellow) fills the lower part, with details of the stomach folds apparent in the upper portion (ribbed appearance). The most usual symptom of a hiatus hernia is gastro-oesophageal reflux, the passage of gastric juice up the oesophagus, due to abnormal anatomy.