A hiatal hernia is different from other abdominal hernias in that the abdominal contents protrude into the chest rather than outside the skin. The diaphragm is a muscle that helps us breath and separates the chest from the abdomen. In some patients, the opening allowing the passage of the oesophagus and stomach becomes loose, resulting in a portion of the stomach protruding into the chest. Occasionally if the opening is large, then other organs such as the spleen, colon, pancreas, or small intestine can also protrude into the chest. Increasing age, obesity, and smoking are known risk factors in adults.