What is acid reflux?

The term acid reflux disease or (GERD) describes any symptomatic condition or histopathologic alteration resulting from episodes of acid reflux. Reflux esophagitis is a condition experienced by a subset of GERD patients with endoscopically evident lesions in the esophageal mucosa. However, acid reflux often causes symptoms in the absence of esophagitis, and 24-hour esophageal pH monitoring can be helpful in identifying this subset of GERD patients. Nonerosive, or endoscopy-negative, GERD patients have reflux symptoms and abnormal esophageal acid exposure during ambulatory 24-hour pH monitoring, but no endoscopic evidence of esophagitis. The acid sensitive esophagus patient is in a subset of the endoscopy-negative GERD population characterized by normal esophageal acid exposure but nonetheless a strong correlation between reflux symptoms and acid reflux events.
Acid reflux disease (GERD) results from the failure of the normal antireflux mechanism to protect against frequent and abnormal amounts of acid reflux (GER), that is, the effortless movement of gastric contents from the stomach to the esophagus. GER is not itself a disease, but a normal physiological process. It occurs in virtually everyone, multiple times everyday, especially after large meals, without producing either symptoms or signs of mucosal damage. In contrast, GERD is a spectrum of disease usually producing symptoms of heartburn and acid regurgitation. Most patients have no visible mucosal injury at the time of endoscopic examination (nonerosive GERD), whereas others have esophagitis, peptic strictures, Barrett esophagus, or evidence of extraesophageal diseases such as chest pain, pulmonary symptoms, or ear, nose, and throat symptoms. GERD is a multifactorial process, one of the most common human diseases, and of economic importance, contributing to the expenditure in the United States of 4 to 5 billion dollars per year for antacid medications.