Hiatal hernia – Symptoms and causes – Mayo Clinic

A hiatal hernia occurs when the upper part of your stomach bulges through the large muscle separating your abdomen and chest (diaphragm). Your diaphragm has a small opening (hiatus) through which your food tube (esophagus) passes before connecting to your stomach. In a hiatal hernia, the stomach pushes up through that opening and into your chest.

https://www.mayoclinic.org/diseases-conditions/hiatal-hernia/symptoms-causes/syc-20373379