A hernia is tissue from inside the abdomen that bulges out through a weak spot in the muscles of the abdominal wall. In a paraesophageal hernia, the stomach bulges up through an opening in the diaphragm (hiatus) alongside the esophagus.

A paraesophageal hernia is not common, but it may occur when the opening in the diaphragm next to the esophagus is abnormally large. The stomach and, rarely, other abdominal organs (such as the intestine, spleen, or colon) may also bulge into the chest cavity with a paraesophageal hernia.

Paraesophageal hernias tend to get worse over time. Surgery is usually necessary to treat the problem, especially if the hernia is causing symptoms.