Ever wonder what your doctor is looking for when examining your esophagus during an endoscopy? In this article, Dr. Chandrasoma takes us on a tour to show the visual symptoms of esophageal cancer and the damage that can develop to the lining of the esophagus. These pictures drive home the point that reflux can cause serious damage to the esophagus, including esophagus cancer, when left unchecked. I hope they motivate you to take control of your health!
The normal esophagus
The normal esophagus is a muscular tube that is lined by a surface epithelium known as non-keratinizing stratified squamous epithelium. This is similar to the surface of the skin except that it does not have the scaly, rough surface of the skin that results from keratinization. The esophageal epithelium is flat, shiny, smooth and has a light tan to white color. This is what it looks like during an endoscopy:
This is what it looks like under a microscope:
This squamous epithelium is beautiful designed to withstand the abrasive effect of food passing down during swallowing. Because it has multiple layers of cells, the surface cells can be lost during swallowing to be rapidly replaced from cells below that continuously multiply to replenish them. Like the skin, which is lubricated by sweat and sebaceous glands, the squamous epithelium of the esophagus is lubricated by mucous glands which keeps the surface moist to facilitate food passing down. The esophagus also has a muscle wall that contracts to push food down from the mouth to the stomach. This is how those layers of cells look under a microscope:
This image shows squamous epithelium lining the interior surface, a mucous gland whose secretion passed up a duct to drain on the surface and lubricate the epithelium. The deepest part of this picture shows part of the muscle wall of the esophagus. Contraction of this muscle propels swallowed food down from the mouth to the stomach.
What happens in GERD?
The squamous epithelium is normally protected from the acid in the stomach by the presence of the lower esophageal sphincter. When the sphincter does not perform its normal protective function and the acid stomach contents reflux into the esophagus, the squamous epithelium becomes damaged by exposure to acid. The degree of damage to the epithelium is dependent on the severity of reflux (i.e. the number of reflux episodes per day, the time the refluxed acid stays in the esophagus, and the acidity of the gastric juice.
Mild acid-induced damage
Mild acid-induced damage to the squamous epithelium produces microscopic changes that can only be recognized if the epithelium is biopsied. Endoscopy can be normal in a person with reflux who has mild damage to the squamous epithelium. Patients with symptoms of reflux who have a normal squamous epithelium on endoscopy are referred to as having “non-erosive reflux disease” or NERD.
Increasing damage to the lining of the esophagus
With increasing damage to the squamous epithelium, erosions (i.e. breaks in the epithelium, like scratches and ulcers in the skin) occur. This is erosive esophagitis. Depending on the severity of the erosive change, reflux esophagitis is classified into grades based on defined criteria in what is called the Los Angeles classification (A, B, C and D grades).
The changes in squamous epithelium produced by acid, including those changes that are not visible at endoscopy, result in symptoms – commonly heartburn. This results when acid (hydrogen ions, which are very small) penetrate into the damaged and more permeable squamous epithelium and stimulate nerve endings. With erosion, nerve endings deep to the epithelium are exposed, which increases the likelihood and severity of the pain.
The changes in squamous epithelium produced by acid are reversible. Neutralizing gastric acid is effective in this regard because acid is the main stimulant for both erosions and heartburn. Effective acid suppression, therefore, allows the erosions to heal, reverses the microscopic changes in the epithelium, and controls heartburn. Modern acid suppressive drugs are highly effective in healing erosive esophagitis and controlling heartburn. However, these drugs achieve this positive change simply by neutralizing the acid; they do not decrease the number of episodes or duration of exposure of the squamous epithelium to refluxed gastric juice. They also do not reverse the damage to the lower esophageal sphincter that is the primary reason for reflux in the first place.
Learn more: The role of the LES
The damage of long-term reflux
With long term reflux, the squamous epithelium undergoes a second type of damage. This is called columnar metaplasia. What this means is that the normal squamous epithelium changes to a columnar epithelium. Columnar surface epithelium, which lines the stomach, is not normally found in the esophagus. This columnar epithelium in the esophagus can be recognized endoscopically as tongues of salmon-pink epithelium that extend up into the white squamous epithelium from the Z-line:
These tongues enlarge both vertically and horizontally with increasing reflux over time. Vertical increase leads to an increased length of columnar epithelium and horizontal increase results in the tubal esophagus becoming circumferentially covered by the columnar epithelium:
Microscopically, this metaplastic columnar epithelium is initially composed of simple mucous cells similar to those lining the surface of the stomach. This is called cardiac mucosa. The majority of patients with small amounts of columnar metaplasia have mainly cardiac mucosa. This is a benign epithelium that has, by itself, no proven risk of malignant transformation in the future.
Intestinal metaplasia – the first early symptoms of esophageal cancer
However, cardiac mucosa can develop a second transformation called intestinal metaplasia. This is characterized by the appearance of cells called goblet cells that are typically seen in the small and large intestine. The presence of intestinal metaplasia in columnar lined esophagus is what defines a patient as having Barrett’s esophagus and an increased risk of future malignancy.
It is important to recognize that endoscopy does not have the capability to accurately differentiate columnar epithelium with and without intestinal metaplasia. Biopsy and microscopic examination by a pathologist is essential for the diagnosis of Barrett’s esophagus.
Learn more: The role of biopsies in the diagnosis of GERD
It can be easy to pass off the symptoms of GERD as annoying, but the reality is that continually exposing the lining of the esophagus to the contents of the stomach can cause serious, irreversible damage. Only a GERD expert can visualize the symptoms of esophageal cancer, but it’s up to you to stop the progression of your condition. Not sure where to start? Learn your reflux disease stage and download your report for personalized ideas for stopping reflux in its tracks: Stage Finder.
We encourage you to learn more about the symptoms of esophageal cancer at the American Cancer Society website.