If you’ve ever had a problem with acid reflux, it’s likely there might be an issue with your lower esophageal sphincter. It’s located between the esophagus and the stomach, preventing food and acid from getting out. The sphincter is controlled by involuntary muscles which move and contract without you consciously activating them.  

Understanding the lower esophageal sphincter, or LES, is crucial to preventing and treating problems associated with reflux and other similar conditions.  

In this guide:

What is the Lower Esophageal Sphincter?

The lower esophageal sphincter (LES) is a muscular valve controlling the bottom end of the esophagus. That’s the food pipe that carries undigested material from your throat to the stomach.  

The LES is also known as the gastroesophageal sphincter. It’s a term that refers to the junction between the two structures, as “gastro” means stomach. Due to its close proximity to the heart, acid reflux in this region can be confused with cardiac pain. That’s why the discomfort is called heartburn. However, the two organs are not connected.  

There’s an upper esophageal sphincter, called the pharyngoesophageal sphincter, that controls the entrance. It prevents air from entering the esophagus when people are talking. Unlike its lower counterpart, the upper sphincter has some conscious control, whereas the LES opens and closes involuntarily.  

How Does the Lower Esophageal Sphincter Work

Usually, the UES and LES work in tandem with muscles in your food pipe that cause rhythmic contractions that move the food downwards. This is known as peristalsis. The sphincters are controlled by nervous signals that determine when the sphincter can open and close.  

As mentioned, the upper sphincter has some input from the person whereas the lower sphincter acts independently. The lower sphincter, like any muscles, can also become weak. If this happens, even if a signal is given, the LES might not have the power to stay closed. If pressure builds in the stomach, then reflux can occur, leading to acid and food in the esophagus.  

People often notice a burning sensation. There may even be an acidic taste, sore throat, and coughing, as the acid irritates your voice box.  

Potential Problems

The lower esophageal sphincter can face several potential issues. Most commonly, reflux happens when food moves from the stomach back up into the esophagus and even the throat. This occurs when then LES fails to close or when pressure on the stomach forces it open. Such regurgitation can be exacerbated if the person has a hiatus hernia. In this condition, the LES and part of the stomach sit above the diaphragm in the chest and not the abdomen.  

Other potential issues include: 

• Achalasia occurs when the LES fails to relax. The food becomes trapped open the LES and cannot enter the stomach. It can create a very strange feeling of discomfort. The condition is diagnosed with an esophageal manometry test.

• Esophagitis is the inflammation of the esophagus. Inflammation can result from repeated acid attacks. If this continues to happen, it can change the cells, increasing the risk of cancer. Alongside esophagitis, esophageal tears can also occur. However, such injuries are relatively rare.

• Dysphagia is a dysfunction of swallowing. A person feels pain when swallowing, often coughing or gagging. There may not be any physical barrier to swallowing, but the pain prevents them from doing so.  

Diagnosis and Testing

If a doctor recognizes the symptoms of an LES problem, they may recommend diagnostic testing. Often people are prescribed anti-acid drugs, like proton pump inhibitors (PPIs) without any testing. However, if there’s a chance something serious is going on, your doctor will want to check.

The most common tests include:

• Barium esophagram. Also known as a barium swallow, the procedure involves taking an X-ray after swallowing barium. This fluid appears opaque on an X-ray, allowing doctors to visualize any abnormalities.

• Upper endoscopy. This procedure involves inserting a camera via the nose or throat to visualize the esophagus and stomach. Some procedures even take a look at the duodenum – the bit after the stomach.

• Esophageal pH monitoring. The test is the gold standard for confirming gastroesophageal reflux disease (GERD). It measures the acidity level around the LES for 24 hours.

• Esophageal manometry. Like the other tests, it can diagnose GERD, as well as achalasia, hypertensive LES, and esophageal spasm. It measures the pressure differences along the entire length of the esophagus or sometimes just around the lower sphincter.

The Functional Gut Clinic offers several types of gastric reflux tests. This includes 24-hour reflux testing to confirm if you’ve got any acid leakage from your stomach and the severity of the problem. Alongside 24-hour testing, we offer esophageal manometry to confirm the underlying problems. It’s the most accurate testing combination to diagnose what’s going on.  

Capsule Endoscopy in Gastrointestinal Disease can also be used to investigate certain conditions of the small intestine, although it's not typically used for diagnosing LES problems directly. 

Treating a Weak Lower Esophageal Sphincter 

Treating a weak LES isn’t as simple as hitting the gym. While it’s a muscle, it cannot be trained by conscious control. That leaves several indirect measures. 

The most common approaches focus on the acid reflux rather than the weak LES. You could take chewable antacids to counteract the acid, or even medications like PPIs to prevent acid production. Lifestyle changes are also effective at reducing stomach acid levels. Fatty, sugary foods increase acid production, while eating before bed can cause late night reflux symptoms.  

Other potential treatments include: 

• Botox injections

• LES dilation

• Surgery 

Summary 

The lower esophageal sphincter, also known as the gastroesophageal sphincter, is your body's natural barrier against acid reflux, sitting between your esophagus and stomach. Getting to know how it works and what can go wrong is key to managing and treating conditions like reflux. Whether through medication or lifestyle changes, understanding this muscle's function can help keep your digestive discomfort at bay, with tests like barium swallows aiding in pinpointing issues.