Is the natural history of the lower esophageal mucosal rings known?
M.Y.M. Chen, D.J. Ott (Winston-Salem)
The mucosal ring was first described by Templeton in 1944  as an annular indentation in the lower esophagus. The presence of a lower esophageal notch was considered uncommon and of no clinical significance. In 1953, Ingelfinger and Kramer  described a contractile ring in the lower esophagus in association with dysphagia. In the same year, Schatzki and Gary  coincidentally published a discussion of the same entity, which they named the lower esophageal ring. Since then many publications about the lower esophageal ring have followed and have discussed the relationship of esophageal rings and dysphagia .
The lower esophageal mucosal ring (LEMR) is generally believed to be a thin membranous ridge of mucosa projecting into the lumen perpendicular to the esophageal wall. The prevalence of mucosal rings varies from 0.2% to 14% in the general population, depending on the technique of diagnosis and the criteria used [5, 6].
The exact location of the LEMR is controversial; some esophageal rings are covered by squamous cell epithelium, and others are layered with columnar epithelium. One explanation for this discrepancy is that during esophageal peristalsis, the lower esophagus shortens and moves orad, and the exact anatomic correlations can be slightly changed during different observations and biopsies. However, most agree that the mucosal ring is located at or adjacent to the squamo-columnar junction, approximately at the distal end of the esophageal vestibule [4, 7, 8]. The upper surface of the ring is usually covered by squamous cell epithelium and its under surface is layered by columnar epithelium. The mucosal ring is also an anatomic demarcation between the esophageal vestibule located above the ring and the stomach positioned below the ring (Figure 1). The esophageal web may mimic an esophageal ring, but the web can be defined as covered solely by squamous epithelium . The esophageal web may be located at any level of the esophagus, whereas the location of the mucosal ring is at the esophagogastric junction (EGJ).
Figure 1. Diagram of lower esophageal mucosal ring. The mucosal ring demarcates the esophageal vestibule located above the ring and the stomach positioned beneath the ring (from  with permission).
The margins of the mucosal ring are typically smooth and symmetric, and its caliber is relatively fixed. Radiologic examination shows a symmetrically smooth ridge, about 2 mm thick, projecting into the esophageal lumen. An esophageal mucosal ring indicates the presence of a hiatal hernia, and may be associated with gastroesophageal reflux (GER), and reflux esophagitis. Surgical specimens of mucosal rings have shown greater or lesser degrees of inflammation and fibrosis. The submucosa of the lower esophagus may also show proliferating connective tissue and numerous lymphocytes and plasma cells [4, 5]. These findings are all consistent with a chronic inflammatory reaction.
The primary symptom of a mucosal ring, if present, is dysphagia. The occurrence and frequency of the episodes of dysphagia depend upon the diameter of the mucosal ring [4, 5, 10]. Many patients with a mucosal ring experience no related symptoms when the mucosal ring is larger than 20 mm in diameter. Dysphagia occurs intermittently in those with mucosal rings between 13 and 20 mm in size, and symptoms are always present in those with rings 13 mm or smaller [4, 5, 10].
Formation of the mucosal ring
The mucosal ring has been considered to be congenital in origin and was briefly thought to represent an overly active lower esophageal sphincter . However, most patients with a mucosal ring are more than 40 years old, and the average age of patients with a mucosal ring is 54 years old; thus, the current consensus is that the mucosal ring is considered an acquired disorder seen in adults . The mucosal ring is rare in infants and children.
The etiology of the mucosal ring is not clear but is generally thought to result from, or be associated with, reflux esophagitis. In 1968, Desai et al.  reported one patient with an 11-year history of reflux symptoms, who developed a 16 mm diameter mucosal ring that was not demonstrated on a previous esophagram. Another patient with heartburn and hiatal hernia developed a 30 mm wide mucosal ring 10 years after the initial normal study .
Natural history of the mucosal ring
The natural history of the mucosal ring has been studied rarely. After the discovery of a mucosal ring, the ring may progressively narrow in size and may change to a distal esophageal stricture. Sometimes the mucosal ring remains stable in caliber which may depend on the status of associated reflux esophagitis. Uncommonly, the mucosal ring may increase in caliber possibly related to effective antireflux treatment or resolution of reflux esophagitis.
Schatzki  reported 66 patients with mucosal rings who were followed up for 5 years. One-third of the symptomatic patients and one-fourth of the asymptomatic patients demonstrated increasing stenosis of their rings compared to the initial measurements. Schatzki  suggested that esophagitis with fibrosis of the esophageal wall was a possible cause of these progressive changes. In our study , two of 22 patients had mucosal rings that developed from a previously normal esophagogastric junction during a 4-year follow-up period (Figure 2).
In the same study , three of 22 patients with mucosal rings showed a decrease in the size of the ring during a follow-up period of 3-5 years, and in two of these patients, symptoms and esophagitis were found at endoscopy. The progressive change of the mucosal ring to a stricture were summarized in one of our previous studies . In that study, a total of eight patients had mucosal rings that were observed to progress to stricture during a 1-5 year period (Figure 3); seven patients had esophagitis that was diagnosed by endoscopy. The progression from mucosal ring to stricture was associated with reflux esophagitis and the change likely resulted from the inflammatory process.
The diameter of the mucosal ring may increase in patients who received antireflux treatment . In one study , the diameter of the mucosal ring increased 3-4 mm over 20-61 months in three of five patients who received antireflux treatment. Two of three patients with mucosal rings that increased in diameter had normal results on 24-hour pH-monitoring studies at the time of the radiologic examination. Two other patients, who received antireflux treatment had follow-up esophageal studies, and the caliber of the mucosal ring remained stable. None of the five mucosal rings in that study disappeared or returned to normal during antireflux treatment.
Figure 2. A 22-mm mucosal ring (A) at the esophagogastric junction compared to normal esophagram (B) with 30-mm EGJ distention taken 4 years previously. (From  with permission.)
Figure 3. A 22-mm mucosal ring (A) in a patient with severe esophagitis who developed a 7-mm-wide esophageal stricture (B) 5 years later (from  with permission).
In summary, the cause of the mucosal ring remains uncertain and its natural history is not well documented. The mucosal ring is likely an acquired abnormality occurring at the esophagogastric junction and possibly related to reflux esophagitis. Solid food dysphagia is the most important symptom associated with the mucosal ring, and the prevalence of this symptom relates to the caliber of the ring. Over time, the mucosal ring will usually remain stable in size or show reduction in caliber and rare conversion to a peptic stricture. The least common temporal observation has been for the ring to increase in caliber although preliminary studies suggest this occurrence after antireflux treatment and resolution of esophagitis. Further investigations will be needed to better define the natural history of the LEMR and the types of treatment that might alter this history favorably.
1. Templeton EE. X-ray examination of the stomach: a description of the roentgenologic anatomy, physiology and pathology of the esophagus, stomach and duodenum. Chicago, III: University of Chicago Press, 1944:104-111.