A hiatal hernia and GERD are related but not the same thing — one is a structural condition, the other is a pattern of symptoms and esophageal damage caused by reflux. Many people with a small hiatal hernia never develop GERD, and plenty of people with GERD don't have a hiatal hernia at all; other factors like LES weakness or delayed stomach emptying can cause GERD independently. Where they intersect is in severity: a hiatal hernia, when present, tends to make reflux more frequent and more difficult to control with lifestyle changes alone, because it removes some of the mechanical support that normally helps the LES do its job. This is why a hiatal hernia is often considered during workup for GERD that isn't responding well to typical treatment — not because it's always the cause, but because it changes what treatment is likely to work.
