A hiatal hernia is where part of the stomach has begun to herniate up into the chest, or travel up into the chest. And so, when we talk about the development of GERD, there can be one or two factors that can lead to that. One would be the reflux valve barrier has broken down, or is not as good as it should be so things are refluxing up. But when you have a hiatal hernia your stomach can be pushed up and trapped, almost in a way that when you swallow food gets stuck in that top part of the stomach where its herniated. It can't really go through because there's a narrow opening that things have to pass though. Your stomach in that area can still produce acid. And so that acid can build up and with that pressure you can get more reflux. That's what a hiatal hernia is. There can be, again, small hiatal hernias; there can be really large hiatal hernias where a significant portion of your stomach, or even other organs, can be pushed up into the chest.