Rings and webs are the most common structural abnormalities of 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, as illustrated below.
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 may only 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. 
The most famous and common ring in the esophagus is the B ring or Schatzki ring, as depicted below.  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, the lower esophageal sphincter, and the 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.  A common complication of Schatzki ring is food impaction, as shown below.
Esophageal rings usually exist as a single lesion but can be multiple, as shown below. 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.  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 at the distal esophagus associated with intermittent dysphagia particularly occurring after swallowing solid foods. [5, 6] Poorly chewed meat can impact at a distal esophageal ring, leading to the term "steakhouse syndrome." 
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.  Schatzki and Gary reported 5 cases with interesting findings, all of which were associated with a hiatal hernia on x-ray film.  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. 
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 the images below.
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, developmental abnormality, inflammation, and autoimmunity.
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. [9, 10]
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.
The link between iron deficiency and esophageal webs remains controversial. Evidence for this theory is limited by the uncertainty in the 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.  Chisholm and associates observed 72 patients with postcricoid webs for 15 years and found iron deficiency in 90%.  However, an epidemiologic study by Elwood et al failed to show a correlation between iron deficiency and cervical esophageal webs. 
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.  Studies are needed to determine if the duration or severity of iron deficient anemia influences web formation with or without dysphagia.
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.
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 diseases have been associated with esophageal webs and include thyroid disease, rheumatoid arthritis, graft versus host disease, Stevens-Johnson syndrome, psoriasis, blistering skin diseases, and pernicious anemia. Patients with PVS have elevated thyroid cytoplasmic autoimmune antibodies of unknown significance. No other autoimmune antibodies have been associated with esophageal webs. More studies are needed to support this casual association.
The cause of esophageal rings and webs remains controversial and can be classified as congenital or acquired.
Acquired causes of lower esophageal rings include gastroesophageal reflux disease (GERD), caustic ingestion, pill-induced inflammation, and mediastinal radiation; an association also exists with some skin diseases. Acquired causes for esophageal webs include PVS, iron deficiency anemia, celiac sprue, inlet patch, graft versus host disease, and skin diseases.
Lower esophageal rings
GERD has been studied as a cause of lower esophageal rings. Symptomatic esophageal rings typically present when an individual is older than 40 years, suggesting that chronic injury from GERD may be involved in the pathogenesis. Although lower esophageal rings are thinner structures than peptic strictures and have no surrounding inflammation, they may be part of the spectrum of GERD-related injury.
Note the following:
In a small retrospective study using endoscopy and barium radiography, Chen et al demonstrated a progression of normal mucosa or lower esophageal ring to peptic stricture in some patients. 
In another study using endoscopy or ambulatory pH monitoring, Marshall et al found GER in 13 of 20 (65%) consecutive patients with symptomatic lower esophageal rings.  Most Schatzki rings are associated with a hiatal hernia, suggesting that GERD may be involved in their pathogenesis.
With regard to esophageal motility, Chen et al found no relationship between lower esophageal rings and esophageal dysmotility or lower esophageal sphincter hypotension.  Evidence exists that acid suppression prevents recurrent symptoms in patients with peptic strictures. Similar studies are needed to demonstrate the effects of acid suppression on symptomatic lower esophageal rings. However, a study by Ott and associates using ambulatory pH monitoring found no difference in abnormal distal esophageal acid exposure in patients with hiatal hernia and lower esophageal rings compared to those with hiatal hernia alone. 
Patients with evidence of Schatzki rings commonly present with gastric acid symptomatology. It has been speculated that acid suppression may reduce the recurrence of Schatzki rings. Dilation followed by acid suppression treatment reduced the risk of recurrence, even in patients without previous reflux symptoms. Sgouros et al observed 44 consecutive patients who underwent dilation of Schatzki rings.  Esophageal manometry and pH studies revealed that 14 had objective evidence of GERD, all of whom were treated with omeprazole. The remaining patients were randomly assigned to omeprazole or placebo. There were no recurrences of Schatzki rings in the group with documented GERD during a mean follow-up of 43 months. Recurrence rates were also significantly lower in the group without objective evidence of GERD who were randomized to omeprazole.
Smith et al evaluated 336 patients with peptic esophageal strictures that were randomized to omeprazole (20 mg daily) or ranitidine (150 mg twice daily) for 1 year after esophageal dilation to 12-18 mm.  Subsequent endoscopy and dilation was performed when clinically indicated. The omeprazole-treated patients required significantly fewer repeated dilation sessions (30% vs 46%) and had improved dysphagia scores compared to the ranitidine-treated group.
The ingestion of alkaline or acidic agents can cause caustic injury to the esophagus. Severe injuries have occurred from ingestion of alkaline agents, such as lye, sodium and potassium hydroxides in oven cleaners, washing detergents, Clinitest tablets, cosmetics, soaps, and button batteries. Ingestion of caustic agents can lead to esophageal stricture. Milder injuries have occurred from ingestion of alkaline agents, such as sodium carbonate, ammonium hydroxide, and bleaches (sodium, calcium hypochlorite, hydrogen peroxide). Toilet bowel cleaners (sulfuric, hydrochloric), antirust compounds (hydrochloric, oxalic), battery fluids (sulfuric), and slate cleaners (hydrochloric) can cause acid injuries. Esophageal strictures from caustic injury develop in 15-38% of cases and occur as early as 2 weeks after caustic exposure.
Uncommon causes of lower esophageal rings include pill-induced esophagitis, rare skin disorders, such as epidermolysis bullosa dystrophica, benign mucous membrane pemphigoid, and mediastinal radiation.
Upper esophageal webs
The association between iron deficiency and esophageal webs is controversial. Chisholm and Jacobs supported this association in 2 case series of 72 and 63 patients. [12, 20] However, a careful epidemiologic study by Elwood failed to show a correlation between iron deficiency and cervical esophageal webs.  Less controversy is found between iron deficiency and dysphagia without webs. Iron deficiency clearly can precede dysphagia. Chisholm and Bredenkamp et al noted resolution of dysphagia but not webs after iron supplementation. [12, 21]
PVS or Paterson-Brown-Kelly syndrome is characterized by postcricoid or upper esophageal webs eccentrically attached to the anterior wall of the esophagus and iron deficiency anemia. Other associated features of PVS are koilonychia, cheilosis, and glossitis. Webs are believed to arise in iron deficiency states. Pharyngeal and cervical esophageal cancers have been associated with PVS. Periodic screening for esophageal cancer in patients with PVS is recommended because of its malignant potential.
Celiac disease or gluten-sensitive enteropathy is characterized by small intestinal malabsorption. Histologic examination reveals a flat mucosal surface with complete absence of normal intestinal villi. Because iron is absorbed predominantly in the proximal small intestine, iron absorption is impaired in celiac disease. Dickey and McConnell described 2 patients with PVS and chronic iron deficiency anemia who were found to have celiac disease by histology.  Dickey and McConnell hypothesized that iron deficiency from celiac disease is the primary cause of upper esophageal webs and PVS. 
Heterotropic gastric mucosa can occur throughout the esophagus, and it is termed an inlet patch if it occurs in the proximal esophagus. The typical location of an inlet patch is usually right below the cricopharyngeal muscle at approximately 20-25 cm from the incisors. Inlet patch has been observed in 2.8% and 3.5% of consecutive endoscopies. On biopsy, corpus-fundic or antral-type mucosa is observed, sometimes containing parietal cells capable of acid secretion. Inlet patches are usually incidental findings, and most cases are believed to be clinically insignificant. Rarely, an esophageal ring and web can be found at the distal margin of the inlet patch, presumably from exposure to acid secretion. See the image below.
Upper esophageal webs have been reported in patients with chronic graft versus host disease after bone marrow transplantation. The mechanism is believed to be the accretion of desquamated esophageal epithelium. Caution is advised when performing endoscopy in patients with esophageal webs and graft versus host disease because of an increased risk of perforation.
Several skin diseases have been reported in association with esophageal webs, including mucous membrane pemphigoid (cicatricial pemphigoid), epidermolysis bullosa, Stevens-Johnson syndrome, and psoriasis. An autoimmune process is believed to be the cause of these associations.
Other esophageal disorders have been reported to be associated with esophageal webs, including Zenker diverticulum, as shown below, and esophageal duplication cyst. The pathogenesis for these associations is unknown.
In patients with multiple esophageal rings, acquired causes include GER and eosinophilic esophagitis. Note the following:
Wong and associates reported abnormal distal esophageal acid exposure in 7 of 9 (77%) patients by ambulatory pH monitoring. 
Siafakas et al reported a case of multiple esophageal rings in an 8-year-old boy with histologic eosinophilic esophagitis who responded to an elimination diet and in whom antireflux treatment failed. 
In a study by Remedios et al, of the patients enrolled, 19 were treated with swallowed fluticasone propionate for 4 weeks’ duration; endoscopic biopsy specimens featured prominent eosinophilic mucosal invasion.  The patients all reported symptoms of dysphagia prior to enrollment. Eleven patients demonstrated complete resolution of symptoms, and all had marked improvement. Four patients demonstrated complete resolution of eosinophil infiltration, and, overall, 18 patients showed significant improvement, according to their biopsy follow-up results.
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.
Race-, sex-, and age-related demographics
To date, no studies have compared 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.  Larger studies are needed to support this observation.
Esophageal rings do not demonstrate a sex preference, but esophageal webs are found mostly in female patients. The reason for this gender 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.
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 have deteriorated.
The international prevalence is unknown.
The prognosis in patients with mild symptoms is excellent, because most respond to dietary modifications and change in eating habits.
Patients with refractory dysphagia usually respond to mechanical esophageal dilation.
Patients with recurrent dysphagia after dilation usually respond to repeat dilation. Surgery rarely is needed.
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 to -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 also rare, but it has been reported. No reports on mortality exist.
Intermittent dysphagia to solid food is the most common complication.
Food impaction, particularly of meat products, is common in patients with lower esophageal rings. Signs of esophageal obstruction are dysphagia and an inability to swallow secretion. This is a medical emergency, and prompt endoscopy with removal of the obstructed food bolus is warranted. Intravenous glucagon is not an effective therapy. To prevent aspiration, barium studies are contraindicated in patients with suspected food impaction.
Spontaneous esophageal perforations have been reported for both esophageal webs and rings. The subgroup of patients who may be at risk of this rare complication is unclear.
Esophageal rings may progress to a stricture, possibly due to underlying GERD. Aggressive GERD management may be needed.
For unknown reasons, patients with PVS are at a higher risk of esophageal carcinoma.
Celiac disease may present as PVS. Test for antigliadin and antiendomysial antibodies. Duodenal biopsy is recommended in patients with PVS.
The following are 3 phases of treatment for patients with symptomatic esophageal rings or webs and chronic GERD:
Phase 1 - Lifestyle modification; weight reduction to ideal body weight; raise the head of bed by 6 inches; stop tobacco and alcohol use; avoid eating less than 2 hours prior to bedtime; limit intake of peppermint, spearmint, spicy food, tomato products, caffeine, and greasy food
Phase 2 - Medical treatment with either an H2-receptor antagonist or a proton pump inhibitor
Phase 3 - Fundoplication surgery
Instruct patients with dysphagia to change their diet and eating habits. A liquid diet is safe. Patients should eat slowly, chew their food carefully, avoid alcohol, and cut food into smaller pieces.
For patient education resources, see Heartburn and GERD Center, Digestive Disorders Center, and Cancer Center, as well Acid Reflux (GERD), Gastrointestinal Endoscopy, Anemia , and Esophageal Cancer (Cancer of the Esophagus).
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