Gastroesophageal reflux disease (GERD): Clinical

The esophagus is a 25-30 centimeter long tube that food and liquids pass through, from the pharynx to the stomach.

The esophageal wall is made of 4 layers: the inner mucosa, which is made of stratified squamous epithelium, except at the lower esophageal sphincter, where it joins the gastric epithelium to form the gastroesophageal junction; the submucosa, a muscular layer; and an outer layer called adventitia.

At the top and bottom of the esophagus there are the upper and lower esophageal sphincters, respectively. Both relax during swallowing to allow the passing of food or liquids, propelled by peristaltic contractions.

Additionally, the lower esophageal sphincter is closed between meals to prevent acid reflux and has a resting pressure of 10 to 45 millimeters of mercury.

When the lower esophageal sphincter pressure is lower than normal, gastric acid reaches the esophagus and the pH of the esophagus drops from 7 to 4, and this is called acid reflux.

Some degree of acid reflux is normal, and it happens mostly after a meal, but it doesn’t cause esophageal damage or associated symptoms.

Gastroesophageal reflux disease, or GERD, happens when the resting pressure of the lower esophageal sphincter is below 10 millimeters of mercury, which allows the backflow of gastric acid in the esophagus, causing esophageal lesions and symptoms that mostly happen at night.

GERD can be caused by a hiatal hernia, where the stomach and lower part of the esophagus slide above the diaphragm and this usually happens in overweight, obese individuals. It can also occur during pregnancy due to increased pressure in the abdomen from the growing fetus.