Esophageal Duplication Cyst

Esophageal duplications and bronchogenic cysts come under the spectrum of foregut duplications, as both take their origins from the primitive foregut (Ponsky and Rothenberg 2009). Esophageal duplications account for up to 20% of benign esophageal lesions and may be associated with other duplications of the intestinal tract and vertebral anomalies (Stringer et al. 1995). Furthermore, one in five cases of alimentary tract duplications is esophageal in origin (Holcomb et al. 1989; Beardmore and Wiglesworth 1958). Esophageal duplications are situated close to and in contact with the esophagus but rarely communicate with it. They are generally isolated congenital malformations in the posterior mediastinum and are occasionally seen with esophageal atresia (Hemalatha et al. 1980; Snyder et al. 1996). Esophageal duplications seen in association with cysts within the vertebral column are called Neuroenteric cysts.

Esophageal duplication cysts were first described by Blasius in 1711. They were further defined by Roth in 1881 who described esophageal duplications as a simple epithelial lined cysts and cysts covered by muscle coat. Often asymptomatic in nature, their true incidence is difficult to establish but is estimated at a frequency of 1:8200 from autopsy studies (Arbona et al. 1984).

During week 4 of gestation, the primitive gut develops an anterior diverticulum which eventually becomes the trachea and respiratory system. At the same time, a posterior bud appears which goes on to become the esophagus. With time, these two systems are separated by the tracheoesophageal septum. As development continues, epithelium obliterates the esophagus before it re-cannulizes. Simple cysts are duplications of the epithelium alone. Several embryological theories have attempted to explain the origins of mediastinal duplications. The esophageal duplication cysts may develop from an accessory diverticulum that may or may not communicate with the esophageal lumen or the failure of appropriate canalization of the gastrointestinal tract. Though these theories may be attractive, neither is able to explain the entity known as Neuroenteric cysts where there is associated vertebral anomaly and a connection between esophageal duplication cysts and cyst within the spinal canal. The split notochord theory attempts to address this by describing a time in embryogenesis where there is persistence of endodermal-ectodermal tract leading to an endomesenchymal tract between amnion and yolk sac (Veeneklass 1952). The postulation in this theory is an incomplete separation of the notochord from the endoderm, and the traction from the developing primitive gut forms a tract between the vertebral column and the duplication. This is described as Neuroenteric cyst. During development, the communication may be lost developing into two distinct cysts: one inside the vertebral column and one close to the alimentary tract. Those cysts not associated with vertebral column anomalies or cysts within the vertebral column may arise during separation of primitive foregut and may give rise to both simple esophageal duplications and bronchogenic cysts. These can explain a variety of epithelia observed during histological examination.

Esophageal duplication cysts can occur anywhere along the length of the esophagus but most commonly occur in the lower esophagus (66%). In the superior mediastinum, duplications can be found on either side of esophagus or in between the trachea and the esophagus. Distally the duplications are situated in the posterior mediastinum and mainly on the right side. They therefore lie in close proximity to the vagus and phrenic nerves, thoracic duct, trachea, and pulmonary vessels. Neuroenteric cysts are associated with vertebral anomalies, in particular hemivertebra, cranial to its location in the mediastinum. The intravertebral and esophageal components may or may not communicate with each other. The recurrent laryngeal nerve should be identified and preserved in cases of an esophageal cyst in the upper and cervical esophagus.

Esophageal duplication cysts are described as being Neuroenteric, cystic, or tubular. They are either encased with a thin layer of muscle or embedded within the esophageal wall itself (Snyder et al. 1996). Esophageal duplications usually replicate histology of the gastrointestinal tract with two layers of muscularis surrounding the luminal epithelial lining and enteric nervous system but do not contain cartilage (Whitaker et al. 1980). Esophageal duplication endothelial lining can be either squamous, gastric, pseudostratified, cuboidal, columnar, ciliated respiratory, pancreatic, or mixed epithelial. The presence of cartilage within its wall indicates bronchogenic origin. Cysts contain either clear mucoid or brown or blood-stained serous fluid. The spinal component of a Neuroenteric cyst has a thin fibrous wall and is lined by single cuboidal layer or pseudostratified epithelium.

Sudden increase in cyst size may occur related to intraluminal bleeding by eroding peptic ulcers related to heterotopic gastric mucosa or infection. These complications can cause retrosternal pain. Erosion or fistulation into the tracheobronchial tree or esophagus can be life-threatening and may present as recurrent pneumonia or hemoptysis (Rhaney and Barclay 1959; Parikh and Samuel 2005). Malignant transformation has been reported in the esophageal duplications as either well-differentiated adenocarcinoma or as squamous cell carcinoma arising in the cyst. The malignant change is rare (Olsen et al. 1991; Chuang et al. 1981; Tapia and White 1985).

Esophageal duplications occasionally share a common muscular wall with the native esophagus. Rarely duplications may be tubular along the entire length of the esophagus and have abdominal extension with duplication of the stomach (Cocker et al. 2006; Shepherd 1965).

Esophageal duplications may remain asymptomatic and present as an incidental finding. Symptoms are known to develop once secretions accumulate within its cavity thus producing a pressure effect on the surrounding organs and esophagus. A sudden increase in the size of the esophageal cyst either as a result of infection or intra-cystic hemorrhage, perforation results in its acute presentation (Nakhara et al. 1990).

Routine antenatal scans detect with increasing accuracy intrathoracic cystic lesions. The postnatal investigation may distinguish some to be duplications or Neuroenteric cyst.

Antenatal

Parikh and Singh describe up to 5% of antenatally diagnosed cystic thoracic lesions as being esophageal duplication cysts, with sudden infant death being reported in those cysts in close proximity of tracheobronchial tree (Parikh and Singh 2011; Fig. 1a, b).

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Incidental

A large number of cysts are asymptomatic from birth. Radiological investigations for unrelated symptoms or blunt chest trauma may therefore reveal a previously unknown duplication cyst (Fig. 2a, b).

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Symptomatic

Symptoms are related to pressure effect from an enlarged esophageal cyst against visceral mediastinum causing stridor, breathlessness, wheezing, or dysphagia (Kawashima et al. 2016). Anemia in 10 of 25 cases, melena in 8/25, vomiting in 8/25, pain in 5/25, and failure to thrive in 4/25 patients were observed by Pokorny and Goldstein 1984. Younger infants are more likely to present with respiratory symptoms. The gastric epithelium may cause peptic ulceration, intra-cystic hemorrhage, and fistulation into the tracheobronchial tree resulting in hemoptysis and pneumonia (Fig. 3a, b). Fistulation into the esophageal lumen leads to hematemesis and melena. The Neuroenteric cysts with an intravertebral component may present with meningitis or neurological symptoms (Piramoon and Abbassioun 1974).

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The order of the radiological imaging is generally guided by the clinical suspicion and presenting symptoms. Antenatally detected cystic lesions should undergo a CT scan of the chest with intravenous contrast. If the postnatal CT identifies a posterior mediastinal cyst / duplication in the chest, an additional abdominal ultrasound, although not specific, may help diagnose associated other gastrointestinal duplications (Fig. 4a).

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Contrast Swallow

A focal smooth compression or displacement may be visible in association with the contrast passing through the esophagus (Fig. 5a–c). Occasionally displacement of esophagus is seen by a posterior mediastinal space occupying lesion. Contrast studies cannot differentiate between the type of lesion causing the external compression and an intramural lesion.

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Thinly lined contrast on the compressing lesion side (Fig. 5c) may suggest a common mucosal wall and should warn operator to be vigilant as during surgery as it may result in esophageal mucosal injury and leak after resection.

Computed Tomography of the Chest with Intravenous (IV) Contrast

If an intrathoracic mass is suspected from preliminary investigations or presenting symptoms, a CT scan is indicated. This will allow the definition, location, and relationship of the mass to be identified, which is important for the surgeon before resection (Figs. 3b, d and 6).

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Duplication cysts on CT scan show as homogenous, smooth bordered, and of low attenuation. In adults, a necrotic paraesophageal posterior mediastinal mass or an abscess is difficult to differentiate by the CT scan alone.

Transesophageal ultrasound can diagnose duplication cysts in adults as compressing cystic lesion containing echogenic material. This investigation is generally not indicated in children.

Esophageal duplications should be resected in symptomatic patients and also in asymptomatic cases to prevent potential life-threatening complications (Holcomb et al. 1989; Dresler et al. 1990; Benedict et al. 2016). Although malignancy is rare, its late presentation causes a significant diagnostic dilemma in adults. Once the diagnosis has been made and location confirmed, complete excision should be undertaken as incomplete resection results in its recurrence. Operative resection can be open or thoracoscopic depending on position of cyst and surgical expertise.

Antenatally diagnosed as well as symptomatic cases in most instances are suitable for thoracoscopic resection with the exception of infected cases with fistulations. Thoracoscopic resection is gaining popularity and has the advantage of less time for recovery and hospital stay, reduced requirement for chest tube drainage, opioid analgesia, and less disfiguring than open operations (Michel et al. 1998; Bratu et al. 2005; Merry et al. 1999).

Two types of esophageal duplications can be encountered; both require slightly different technique during resection. The esophageal duplication with its own separate muscle wall attached with the native esophagus with loose connective tissue. A second variety is rare but may pose a surgical challenge during its resection. This duplication on the side of the native esophagus is not covered by the muscle coat and attached to each other by their mucosa.

Thoracoscopic approach is ideally suited for the resection of esophageal duplications as it is associated with low morbidities (Bratu et al. 2005; Merry et al. 1999). Many including our center have stopped placing a postoperative chest drain in uncomplicated resections. Infradiaphragmatic duplications are resected laparoscopically.

Thoracotomy is advised for complicated duplications involving fistulation into the tracheobronchial tree. Previous inadequate resection with recurrence may require an open approach for a complete resection. Cervical duplication will require a cervical incision for its resection.

Esophageal duplications, once identified, should be electively resected due to their potential to cause complications: related peptic ulcers from heterotopic gastric mucosa, bleeding, and perforation, pressure symptoms on airway causing stridor, and infection causing recurrent pneumonia and mediastinitis. Neuroenteric cysts may result in meningitis and spinal cord compression if left untreated, causing neurological deficit. There is also the potential long-term risk of malignancy. Thoracoscopic excision in an asymptomatic patient has a lower complication rate than surgery for a symptomatic cyst. Incomplete excision results in a recurrence and will require further surgery.

As minimally invasive technique becomes widely available and practiced in future, most surgeons will be able to offer thoracoscopic surgery to children presenting with esophageal duplication cyst.