Hiatal hernia: An anatomical abnormality in which part of the stomach protrudes up through the diaphragm into the chest.
Normally, the esophagus passes down through the chest, crosses the diaphragm, enters the abdomen through a hole in the diaphragm called the esophageal hiatus and joins the stomach just below the diaphragm. When there is a hiatal hernia, the opening of the esophageal hiatus is larger than normal and a part of the stomach slips up or passes (herniates) through the hiatus and into the chest.
This type of hernia can be congenital (present at birth) or acquired over time. Symptoms usually start with a tingling or burning sensation, heartburn, or gastroesophageal reflux (GERD). These may require surgery, which may be emergent if blockage of the esophagus or pain is present.