Duplication Cyst

Etiology

Although the exact cause of alimentary tract duplications is unknown, these are believed to occur due to embryological aberrations between the 4th and 8th weeks of gestation. Multiple theories have been put forward to explain its etiopathogenesis. The split notochord theory is based on the abnormal separation of the growing notochord from the endodermal cells. This theory is mostly cited to explain the occurrence of vertebral anomalies associated with duplication cysts.[1] 

The recanalization theory postulates that errors in the gut's recanalization are responsible for these cysts' occurrence.[1] However, it fails to explain the occurrence of duplications in the areas that do not undergo the process of recanalization during their embryological development. The embryonic diverticula theory is based on the explanation that some diverticulae exist in the growing embryo. A persistent diverticulum grows with the growth of the alimentary tract and contributes to the genesis of alimentary tract duplication. Although it gives a fair justification of the mechanism behind the occurrence of the majority of the duplication cysts, it fails to explain the reason for heterotopic mucosa in these cysts.[1][2] 

The partial or abortive twinning theory explains that these duplication cysts occur due to incomplete twinning of the alimentary tract.[1] The association of doubling anomalies of the genitourinary tract with colorectal duplication cysts justifies the theory; however, it fails to explain the occurrence of these cysts in other areas.

Epidemiology

The incidence of alimentary tract duplications is 1 in 4500 births. A slight male preponderance has been observed with these cysts.[3] They are mainly detected in childhood, with most duplications symptomatic within the first 2 years of life. However, late presentation in adulthood is also seen.[4]

Pathophysiology

Three distinct characteristics of these cysts include an epithelial lining representing a part of the gut, a well-defined layer of smooth muscle, and a close approximation with some part of the gastrointestinal tract, such as sharing a common wall.[1] 

Cysts can be divided into cystic or tubular based on their structural configuration. Cystic duplications (80%) are more common and do not communicate with the bowel lumen. Tubular duplications are less common and communicate with the lumen of the bowel.[4] 

These cysts can be divided into foregut, midgut, and hindgut duplications depending on the part of the alimentary tract they are intimately attached to. The ileum, followed by the esophagus, is the most common location for these duplication cysts.[1] Depending on their embryological origin, the foregut duplications can be further divided into esophageal, bronchogenic, and neurenteric.[4]

Histopathology

On histopathology, a distinct mucosal lining and smooth muscle coat are characteristic features of these cysts. The mucosal lining generally corresponds to some part of the gastrointestinal tract. The mucosal lining may be heterotopic and unrelated to the adjacent bowel. Ectopic gastric mucosa is seen in approximately 20% to 30% of the cases and is common in esophageal and midgut duplication cysts. Pancreatic mucosa is commonly observed in gastric duplications. Besides, bronchogenic cysts have respiratory epithelium, cartilage, and bronchial submucosal glands.[1][4]

History and Physical

The majority of the cases have an alimentary tract duplication present within childhood. The type of symptoms depends on the location of the cyst, the type of the cyst (cystic or tubular), and the presence or absence of ectopic mucosa. Patients with cystic duplications are generally symptomatic with abdominal pain but can also be incidentally detected. Partially communicating (with only one end communicating with the adjacent bowel), tubular duplications cause symptoms such as chronic constipation due to the loading of the intestinal contents in a blind loop. Cysts with heterotopic gastric or pancreatic mucosa present as abdominal pain and gastrointestinal bleeding due to ulceration and bleeding of the healthy adjacent bowel.

Clinical Presentation

Based on the location of the cyst, the clinical presentation may vary.

Foregut duplication cyst

Dysphagia, vomiting, epigastric pain, and upper gastrointestinal bleeding are common clinical manifestations of esophageal duplication cysts. They can also cause compression on the surrounding structures and present as a large neck mass, stridor, dyspnea, cough, etc. Patients with bronchogenic cysts also present with similar features of dysphagia, chest pain, cough, dyspnea, etc. Foregut duplication cysts can also be prenatally detected on a routine ultrasound. Features can be observed, including intrathoracic mass, polyhydramnios, mediastinal shift, and hydrops. Gastric duplication cysts are rare and usually present with abdominal pain, vomiting, abdominal mass, and features of gastric outlet obstruction.[4] Duodenal duplication cysts may present as abdominal pain, nausea, vomiting, jaundice, and upper gastrointestinal bleeding. Rarely, they may present with features of acute pancreatitis.[5]  

Midgut duplication cyst

Children with small bowel duplications usually present with abdominal pain, palpable mass, nausea, and vomiting. They may present with features of upper gastrointestinal bleeding due to heterotopic mucosa. Acute abdominal pain due to intussusception or volvulus is also reported in the literature.

Hindgut duplication cyst

Colonic duplication cysts are rare compared to small bowel duplication cysts. They usually contain colonic mucosa; however, some cases with ectopic mucosa have also been reported. Similar to small bowel duplication cysts, these may present as abdominal pain, palpable mass, vomiting, gastrointestinal bleeding, or features of intestinal obstruction. Malignant transformation has also been seen in these cysts. In addition, rectal duplications can present with distinct clinical presentations, including presacral masses, imperforate anus with rectovaginal fistula, etc.[4][6]

Evaluation

A prenatal diagnosis from an ultrasound examination is possible for these lesions. However, the sensitivity is only 20% to 30%.[1] Due to a varied clinical presentation, radiological investigations play a vital role in diagnosing duplication cysts. Ultrasound of the abdomen shows a classical five-layered cyst wall with alternating hyperechoic and hypoechoic layers. This is known as the gut signature sign and is pathognomonic for alimentary tract duplication. Although ultrasound can also diagnose foregut duplications in the neck, its sensitivity is poor for intrathoracic lesions. Transesophageal ultrasound (TEE) can be used for these lesions, but it is not readily available at all centers, especially in developing countries. Contrast-enhanced computed tomography (CECT) can localize the lesions in these scenarios. On CECT, these duplications appear as hypoattenuating masses with an enhancing rim. Similar to intrathoracic lesions, localizing and diagnosing rectal duplication cysts deep in the pelvic cavity might be difficult. Magnetic resonance imaging (MRI) provides better cross-sectional anatomy in these cases and helps diagnose duplication cysts involving the hindgut.[1]

A technetium-99m pertechnetate scan can be done to determine whether the cyst contains ectopic gastric mucosa. Although it might not change our management, it can help diagnose multiple synchronous lesions. It is better to know about duplication cysts that rarely show a positive pertechnetate scan, like bronchogenic and rectal duplication cysts. This radionuclide scan can, therefore, be avoided in these cases.

Treatment / Management

The definitive treatment for a duplication cyst is surgery. Depending on the surgeon's expertise, the surgical approach can be open (laparotomy or thoracotomy) or minimally invasive (laparoscopic or thoracoscopic).

Management of Antenatally or Incidentally Diagnosed Asymptomatic Lesions

Antenatal ultrasound can diagnose these anomalies, and early surgery should be done. This is not only due to malignant transformation but also, if left untreated, a significant proportion of these cases may develop complications such as intussusception, volvulus, hemorrhage, etc.[1]

Symptomatic cases

Early surgery is recommended in all symptomatic cases.

Intrathoracic esophageal duplication cysts

These require a posterolateral thoracotomy. These can be removed by simple excision. In large cysts, decompression of the cyst may help in the better dissection of the cyst.

Gastric and intestinal duplication cysts

Laparotomy with excision of the cyst can be done in the majority of cases. Resection with end-to-end anastomosis might be required in tubular duplications or those intimately associated with the bowel wall. Long tubular or multiple duplications involving the small intestine can be removed by performing mucosal stripping or Wrenn's procedure.[7] Similarly, long tubular duplications of the colon can be taken care of by performing Soper's procedure.[8] Communication is established between the distal blind duplication and healthy bowel to evacuate stools. (B3)

Rectal duplication cysts

These cysts might present as presacral masses or imperforate anus with rectovaginal fistula. Therefore, these may require a posterior sagittal or abdominoperineal approach for cyst excision.

Special Scenarios 

Synchronous cysts in the thorax and abdomen

Synchronous lesions are seen in 10% to 15% of the cases.[9] In the condition of synchronous cysts, it is valid to excise the symptomatic one first. However, if both are symptomatic, the thoracic cyst can be excised first to minimize the anesthesia-related issues. It must be remembered that both cysts can be excised in a single sitting with modern anesthesia. However, this increases morbidity, leading to the risk of postoperative mechanical ventilation, the prolonged requirement of analgesics, prolonged hospital stay, etc.(B3)

Neurenteric cysts

Proper evaluation with a spine MRI and surgical planning with the neurosurgery team are crucial. If the intraspinal component is significant, it should be removed first.

Differential Diagnosis

The differential diagnoses for duplication cyst include the following:

• Meckel's diverticulum: It presents in a similar age group and has a similar presentation of abdominal pain and upper gastrointestinal bleeding. A pertechnetate scan can be positive in both scenarios. However, a definite diagnosis is established only on exploration. The distinct difference is location. Duplication cysts are located on the mesenteric side, while Meckel's diverticulum is on the anti-mesenteric side.
• Congenital segmental intestinal dilatation: Characterized by a segmental dilatation of the small or large intestine up to 3 to 4 times. Although dilatation can be seen in both duplication cysts and congenital segmental dilatation, the difference between these 2 is the lack of any cystic structure adjacent to the normal bowel in segmental dilatation. However, the treatment of both is similar.[10]
• Other intraabdominal cystic lesions: These include mesenteric, omental, choledochal, ovarian, etc.
• Presacral masses: Rectal duplication cysts can mimic other presacral masses, including sacrococcygeal teratoma, anterior meningocele, dermoid, etc. MRI and biochemical tests, including alpha-fetoprotein assay, usually help in definite diagnosis.
• Other intrathoracic cysts: Other intrathoracic cysts, including the pericardial and thymic cysts, may be considered close differentials of duplication cysts. However, these are located in the middle and the anterior mediastinum, respectively, unlike the duplication cyst, which is located in the posterior mediastinum.

Prognosis

Alimentary tract duplication cysts are commonly seen in children. Surgical resection is required in the majority of cases. However, a proportion of cases may require complex surgeries. Excellent long-term outcomes are reported after optimal surgery.

Complications

Delayed diagnosis and surgery can lead to complications, including volvulus, intussusception, recurrent hemorrhage, and risk of malignant degeneration etc.[1] Perforation of large duplication cysts has also been reported in the literature.[11] Complications after surgery are similar to any other laparotomy, including a spectrum ranging from localized wound infection to anastomotic leak and adhesive obstruction.