Here's additional info: A hernia is the pressing of an organ through an abdominal opening in the muscle wall of the cavity that protects it. With a hiatal hernia, a portion of the stomach pushes through a teardrop-shaped hole where the esophagus and the stomach join. The most common cause of a hiatal hernia is an increase in pressure on the abdominal cavity. Pressure can come from coughing, vomiting, straining during a bowel movement, heavy lifting, or physical strain. Pregnancy, obesity, or excess fluid in the abdomen also contribute to hiatal hernias.