LES: A Tale of Two Sphincters
In order to further understand how we make treatment decisions, let’s go back again into the lower esophageal sphincter. Now, we have already discussed the fact that the disease is caused by a progressive degeneration.
But what are we really talking about when we refer to the LES, or the lower esophageal sphincter? Many think that it’s a single sphincter, but in reality, it is actually a dual sphincter mechanism. So there is what is commonly thought of as the lower esophageal sphincter, which is a specialized muscle layer that we refer to as the muscularis propria, that is within the wall of the esophagus and the upper portion of the stomach known as the cardia. This specialized muscle is what’s responsible for contracting and maintaining the pressure.
However, that’s just what we call, now, the internal sphincter. There is also an extrinsic or an external sphincter that works in coordination with that same internal sphincter. The external sphincter is actually made up of a portion of the diaphragm, which wraps around the bottom of the esophagus, just above the stomach.
The vagus nerve, which enervates the esophagus and helps determine motility in the esophagus and the stomach, as well as things like your heart rate, coordinates the action between the external and the internal portions of the sphincter, so that when one contracts, the other one contracts simultaneously. Similarly when one loosens, the other will loosen simultaneously. This is what allows us to swallow normally.
It is the coordinated action of these two sphincters that helps to prevent reflux. Thus it is important when we think about treatment to decide which of these two sphincters, either the internal or the external or perhaps both of the sphincters, are malfunctioning, so we can better design the treatment for your reflux disease.
This is known as personalized medicine, or subtyping the disease, so that we can decide what is the best treatment.