Gastroesophageal reflux disease

Gastroesophageal reflux disease is what happens when the contents of the stomach travel backward, up into the esophagus, the tube that food goes down. Those contents irritate and eventually inflame the esophageal mucosa, the layer that lines the esophagus on the inside.

Between the two there is a door, the lower esophageal sphincter, a ring of muscle that is normally closed. The most common mechanism of reflux is that this ring relaxes at moments when it should not. The door between the esophagus and the stomach opens at the wrong time. Up through it come gastric acid, peptic enzymes, which digest proteins, and bile acids.

A hiatal hernia makes that arrangement worse. It occurs when part of the stomach slides upward through the opening in the diaphragm, the muscle that separates the chest from the abdomen. That throws off the relationship between the diaphragm and the sphincter, and the hernia also works as a holding pouch for gastric contents that can reflux when the sphincter relaxes during swallowing.