Excerpt from Esophageal Webs and Rings

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Background

Rings and webs are the most common structural abnormalities in the esophagus. The terminology, pathogenesis, and treatment of these esophageal lesions remain controversial. The terms rings and webs often are used interchangeably in the literature. The pathogenesis and treatment of esophageal rings and webs are evolving. Most of these structural lesions are asymptomatic but can cause dysphagia. This review attempts to provide a practical update on esophageal rings and webs and to discuss their definition, epidemiology, pathophysiology, clinical presentation, differential diagnosis, diagnosis, treatment, and follow-up care.

An esophageal ring is defined as a concentric, smooth, thin (3-5 mm) extension of normal esophageal tissue consisting of 3 anatomic layers of mucosa, submucosa, and muscle. An esophageal ring can be found anywhere along the esophagus, but it usually is found in the distal esophagus. Three types of esophageal rings exist, and they are classified alphabetically as A, B, and C (see Media file 1).

The A ring is uncommon and represents a muscular ring several centimeters proximal to the squamocolumnar junction (SQJ). This muscular ring is not a fixed structure and only may be demonstrated in some barium swallows. It is located approximately 1.5 cm proximal to the SQJ, and it is rarely symptomatic. Some debate surrounds the existence of the A ring as a separate entity. Hirano et al described a unique manometric pattern of peristaltic, high-amplitude, long-duration, and multiple peaked esophageal contractions in 3 men with A rings.¹

The most famous and common ring in the esophagus is the B ring or Schatzki ring (see Media files 2-3). By definition, the Schatzki ring is a web because it is composed of only mucosa and submucosa. Typically, the Schatzki ring is located at the SQJ, and it marks the proximal margin of a hiatal hernia. Autopsy examinations support that the free margin of the Schatzki ring marks the SQJ. Because of the difficulty in accurately locating the SQJ, lower esophageal sphincter, and lower esophageal ring during swallowing, the exact anatomic relationship between the esophageal ring and the SQJ remains controversial.

Some authors believe the Schatzki ring is a protective barrier against gastroesophageal reflux (GER), while others, such as Winters et al, question the protective nature of rings.² A common complication of Schatzki ring is meat impaction (see Media file 4). Esophageal rings usually exist as a single lesion but can be multiple (see Media file 5). Several names have been coined for when multiple rings are found in the esophagus, including multiple esophageal rings or webs, congenital esophageal stenosis, ringed esophagus, corrugated esophagus, and feline esophagus.

In 1944, Templeton first described the esophageal ring as a weblike membranous ring in the lower esophagus.³ Prior to 1953, all webs were found in infants and children and were believed to be congenital. In 1953, the term ring became popularized because of its association with dysphagia. During this time, Ingelfinger and Kramer as well as Schatzki and Gary separately reported a group of adults older than 50 years with x-ray findings of a ringlike narrowing of the distal esophagus associated with intermittent dysphagia particularly occurring after swallowing solid foods.^{4, 5} Poorly chewed meat can impact at a distal esophageal ring, leading to the term "steakhouse syndrome."⁶

Ingelfinger and Kramer reported 6 cases of esophageal rings, and examination of 1 of these rings following esophageal resection revealed a circle of hypertrophied muscle underlying normal esophageal mucosa.⁴ Schatzki and Gary reported 5 cases with interesting findings, all of which were associated with a hiatal hernia on x-ray film.⁵ Partial excision of one of these rings exhibited involvement of mucosa and submucosa only. In 1968, a subsequent analysis of 64 pathologic cases of lower esophageal rings by Miller and Wichern showed that none of the rings had muscle wall involvement, except for the 1 case from Ingelfinger and Kramer.⁷

The C ring is a rare anatomic finding on radiographic studies referring to the indentation caused by the diaphragmatic crura. It is rarely symptomatic.

An esophageal web is a thin (2-3 mm), eccentric, smooth extension of normal esophageal tissue consisting of mucosa and submucosa that can occur anywhere along the length of the esophagus but is typically located in the anterior postcricoid area of the proximal esophagus (see Media files 6-7). 

See related CME at Diagnostic Evaluation of Dysphagia. 

Pathophysiology

The pathophysiology of esophageal rings and webs is controversial. Several theories have been proposed for the formation of esophageal webs and rings. These include etiologies related to congenital origin, iron deficiency, development, inflammation, and autoimmunity.

Congenital theory

Rings and webs may represent a remnant of embryologic development in which the esophagus fails to recanalize completely. In children, fragments of cartilage in esophageal ring-like structures similar to trachea have been described. Fonkalsrud and Anderson reported ciliated pulmonary epithelium and bronchial remnants in resected specimens; however, the fact that most patients with symptoms present when they are older than 40 years suggests that rings and webs alone do not produce any symptoms.^{8, 9}

Publications in pediatric radiology have suggested that Schatzki rings are more common in children than once thought. Most children are asymptomatic, and, thus, they are probably far less detected than indicated. These findings might support the theory that the pathophysiology of the rings contains a congenital factor.

Iron deficiency

The link between iron deficiency and esophageal webs remains controversial. Evidence for this theory is limited by the uncertainty in duration of iron deficiency necessary for web formation. Another challenge to this theory is that most esophageal webs are asymptomatic. In rabbits that were iron deficient, histologic examination of esophageal muscle revealed muscle fiber abnormalities. This histologic finding suggests that myasthenic changes in esophageal muscles may lead to dysphagia.

In patients with postcricoid webs and Plummer-Vinson syndrome (PVS), histologic findings of hyperplasia degeneration of mucosa have been reported and attributed to iron deficiency. Okamura hypothesized that mucosal degeneration can lead to a cascade of decrease in swallowing, restriction of esophageal wall dilation, repetitive tissue injury and healing, and, eventually, permanent esophageal mucosal changes, such as a web.¹⁰ Chisholm and associates observed 72 patients with postcricoid webs for 15 years and found iron deficiency in 90%.¹¹ However, an epidemiologic study by Elwood et al failed to show a correlation between iron deficiency and cervical esophageal webs.¹²

Other nonsupportive studies include the equal likelihood of esophageal webs in patients who are iron deficient and in controls, lack of anemia in most patients with esophageal webs, and resolution of dysphagia but not webs following iron therapy. Further, Chisholm reported only a 10% prevalence of esophageal webs in patients who were iron deficient.¹¹ Studies are needed to determine if the duration or severity of iron deficient anemia influences web formation with or without dysphagia.

Developmental theory

Esophageal rings have been postulated to occur during development when a pleat of mucosa is formed by infolding of redundant esophageal mucosa due to shortening of the esophagus. The cause for the repeated plication is unknown.

Inflammation theory

Inflammatory cells can be found in biopsy specimens of esophageal rings and webs. These inflammatory cells are more common in distal esophageal lesions than in proximal esophageal lesions. The presence of neutrophils suggests an acute inflammatory response to a variety of insults, including GER, medications, caustic ingestion, radiation, and trauma. Eosinophil infiltration suggests a cause from GER, allergic response (food), and idiopathic eosinophil gastroenteritis. The finding of lymphocytes and plasma cells suggests chronic inflammation.

Autoimmune theory

Frequency

United States

The true prevalence of esophageal rings and webs is unknown because most of these lesions are asymptomatic. Lower esophageal rings are found in 6-14% of routine barium radiographs for various reasons. In patients with dysphagia, esophageal webs can be found in 5-15% by barium radiography. For patients with multiple esophageal rings and webs or congenital esophageal stenosis, esophageal webs and rings are estimated to occur in 1 in 25,000 to 1 in 50,000 live births.

International

The international prevalence is unknown.

Mortality/Morbidity

Most patients with esophageal rings and webs are asymptomatic. Schatzki reported a direct correlation between the luminal diameter of an esophageal ring and patients' symptoms. Almost all patients with an esophageal lumen less than 13 mm have dysphagia. Patients with esophageal lumen from 13-20 mm may or may not have dysphagia, and if the luminal diameter is greater than 20 mm, dysphagia is rare. Spontaneous perforation of the esophagus is rare, but it has been reported. No reports on mortality exist.

Race

To date, no studies compare racial prevalence; however, esophageal rings and webs appear to predominantly affect white individuals. Wong et al reported 13 patients with multiple esophageal rings, and all were white.¹³ Larger studies are needed to support this observation.

Sex

Esophageal rings do not demonstrate a sex preference, but esophageal webs are found mostly in female patients. The reason for this difference is unknown, but population studies suggest iron deficiency, particularly in menstruating females, may be a cause. However, for unknown reasons, multiple esophageal rings are found predominantly in young males.

Age

Rings and webs have been identified in all age cohorts. Patients do not typically become symptomatic until after the age of 40 years. Dysphagia is a very common occurrence in the elderly. Oropharyngeal and dental problems may exacerbate symptomatic rings in the elderly, as their ability for mastication and swallowing are deteriorated.

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