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Thứ Hai, 29 tháng 7, 2013

GASTRIC DUPLICATION CYST @ MEDIC


Male patient 26yo from An Giang province complaints of nausea. Endoscopy revealed a submucosa mass at posterior antrum, which was confirmed later by CT,  but cannot rule out a heterotopic pancreas.










Ultrasound detected a cystic mass from greater curvature which has cyst wall like gastric wall and no debris inside.




Transversal section at antrum= Water filling helps viewing clearly root of gastric duplication cyst which continued greater curvature of stomach. The cyst wall has 2 layers: hypoechoic muscularis and hyperechoic lining mucosa [muscular rim].  

Our present case has these criteria : (a) the wall of the cyst is contiguous with the stomach wall; (b) the cyst is surrounded by smooth muscle, which is continuous with the muscle of the stomach; and (c) the cyst wall is lined by epithelium of gastric or any other type of gut mucosa.


The gastric duplication cyst has clearly muscular rim with size of 27.1x15.6mm without debris inside.

The hypoechoic muscularis of the gastric antrum appears to be contiguous with the hypoechoic rim of the cystic lesion (white arrow).




A video clip of gastric duplication cyst on ultrasound examination.

video



So it is a noncommunicating gastric duplication cyst with the gastric lumen. Patient underwent surgery to remove the gastric duplication cyst on 20/8/2013 with the normal pathological report. After 3 months of operation he remains well and endoscopy shows a gastric scar on posterior surface of his stomach.




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Explanation (from Chavira, http://pediatricimaging.wikispaces.com/Chavira-001-Gastric+Duplication+Cyst)

Gastrointestinal duplication cysts occur in 1 in 4500 births, of these 75% are intraabdominal, 20% thoracic, and 5% thoracoabdominal. Gastric duplication cysts, in particular, are one of the most rare comprising 7% of all gastrointestinal cysts. Other locations include the jejunum/ileum (53%), esophagus (18%), colon (13%), and duodenum (6%). Gastric duplication cysts are often a missed diagnosis because of their rarity and vague clinical presentation.

Duplication cysts arise due to a congenital developmental abnormality within the gastrointestinal tract, of which the etiology is not completely understood. Multiple theories have been developed to explain their existence including partial twinning, in utero ischemic events, and abnormal endoderm and notochord separation. Bremer's theory of abnormal recanalization has also been described to explain their occurrence. A brief review of the embryology related to the development of the alimentary tract helps to better understand this theory.

During the 6th week of gestation, epithelial cells proliferate and the lumen of the GI tract becomes occluded. Vacuoles are then created which fuse with one another to recanalize the lumen. Abnormal development of the gastrointestinal lumen can occur when a group of vacuoles coalesce with one another but do not form a connection with the developing lumen, with continued growth a wall of bowel will then form between them, which may lead to the formation of a duplication cyst not in communication with the gastric lumen. Conversely, if a small group of vacuoles coalesce and one opens into the main lumen, the duplication cyst may form in communication with the gastric lumen. 


Image 1. Normal and abnormal development of the gastrointestinal lumen are depicted in the above image.

It is important to note that although each theory offers an explanation for the formation of duplication cysts, there is no singly theory that can adequately explain the occurrence of all forms of duplication cysts.

The presentation of duplication cyst depends on the size and location. The typical presentation is in a child less than 2 years of age with females being more commonly affected than males. However, adult cases have been reported. The typical symptoms are nausea, vomiting, and a palpable abdominal mass. However, in some cases patients may be entirely asymptomatic. The features characteristic of a duplication cyst include a well-developed coat of smooth muscle, an epithelial lining the same as that of the alimentary tract, and an attachment or prior attachment to a part of the alimentary tract. The location of the cyst is typically along the greater curvature and most are not in communication with the gastric lumen.

The diagnosis of a duplication cyst is usually made with CT and US imaging. Ultrasound is becoming the preferred diagnostic imaging tool, as in some cases it may reveal the "double wall sign" outlining the echogenic inner layer and hypoechoic outer muscular layer which is characteristic of a duplication cyst. In some cases, however, imaging is not sufficient and the diagnosis is confirmed intraoperatively.

Treatment for gastric duplication cyst is surgical. The excision of a gastric duplication cyst can usually be done with minimal loss of adjacent stomach. However, if the duplication cyst and gastric lumen are in communication, partial gastrectomy is required. Complications that may occur if untreated include perforation and ulceration. There is also a risk of malignant transformation.
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 From Review of Radiology, DAHNERT.

Gastric duplication cyst = intramural gastric cyst lined with secretory epithelium

Incidence: 7% of all alimentary tract duplications

Path: noncommunicating spherical cyst (majority); may communicate with aberrrant pancreatic duct; ectopic pancreatic tissue found in 37%

Symptomatic age: infancy; in 75% detected before age 12; M:F = 1:2

• pain (from overdistension of cyst, rupture with peritonitis, peptic ulcer formation, internal pancreatitis)

• vomiting, anemia, fever

• symptoms mimicking congenital hypertrophic pyloric stenosis (if duplication in antrum / pylorus)

Most common site: greater curvature (65%)

- paragastric cystic mass up to 12 cm in size, indenting greater curvature

- seldom communicates with main gastric lumen at one or both ends

- may enlarge + ulcerate

- Tc-99m uptake



US:

+ cyst with two wall layers (inner echogenic layer of mucosa, outer hypoechoic layer of muscle)

+ clear / debris-containing fluid


Cx:

(1) Partial / complete small bowel obstruction

(2) Relapsing pancreatitis (with ductal communication)

(3) Ulceration, perforation, fistula formation

DDx: pancreatic cyst, pancreatic pseudocyst, mesenteric cyst, leiomyoma, adenomatous polyp, hamartoma, lipoma, neurofibroma, teratoma


Discussion

Gastrointestinal duplication is a relatively rare anomaly that may occur at any level from oral cavity to rectum with ileum being the most common site. Duplication cysts of the stomach are quite rare, and most of them have been reported in children [1, 5, 6]. Duplication cysts of ileum are usually located on mesenteric border [7], whereas the usual location for gastric duplication cysts is along the greater curvature [4, 6, 7]. The duplication cyst is entirely separated from the adjacent bowel but shares a common wall [8].The essential criteria for diagnosis of a gastric duplication cyst are (a) the wall of the cyst is contiguous with the stomach wall; (b) the cyst is surrounded by smooth muscle, which is continuous with the muscle of the stomach; and (c) the cyst wall is lined by epithelium of gastric or any other type of gut mucosa [1, 4, 9].

Our present cases fulfilled these criteria excluding other diagnoses.

Gastric duplication cysts comprise 4% of all gastrointestinal duplications. Various other congenital anomalies such as alimentary tract duplications, esophageal diverticulum, or spinal cord abnormalities are encountered in up to 50% patients [8]. These malformations are believed to be congenital, formed before the differentiation of epithelial lining, and therefore named for the organ with which they are associated [3, 10]. Duplications result from the disturbances in embryonic development, and various theories have been proposed for the actual mechanism. Bremer proposed the theory of errors of recanalization and fusion of longitudinal folds. He suggested that duplication cysts originated from the fusion of longitudinal folds allowing the passage of a bridge of submucosa and muscle at the second and third month of intrauterine life [5]. McLetchie suggested that adhesion of notochord and embryonic endoderm might not elongate as quickly as its surrounding structures, causing traction diverticulum leading to duplication cyst formation [5]. Other theories of enteric duplication include abortive twinning, persistent embryological diverticula, and hypoxic or traumatic events [5]. There is no single theory that is satisfactory for all types of duplications [5].

Greater than 80% of gastric duplications are cystic and do not communicate with lumen of the stomach. The remainders are tubular with some communication [5]. The structure is defined as tubular when the lumen is contiguous and cystic when the lumen is not contiguous with stomach lumen [6]. The mucosal lining of duplication may be histologically similar to the segment of gut to which is topographically related.

However, some duplications may include lining from other segment of alimentary or respiratory tract. The presence of respiratory epithelium in the cysts of thorax, tongue, liver, and stomach suggests that the undifferentiated epithelium of foregut might undergo transition to differentiated specialized epithelium during embryonic period [5].

Gastric duplications typically become symptomatic during childhood. 67% are diagnosed within the first year of life, and less than 25% are discovered after age 12 [4]. The duplication cysts of the stomach are usually diagnosed intraoperatively in adults [10]. In our first patient, the preoperative CT and MRI findings were interpreted as being most consistent with a pancreatic neoplasm, and diagnosis of GDC was suspected only during surgery. The clinical presentation of gastric duplication cysts can be highly variable and nonspecific ranging from vague abdominal pain to nausea, vomiting, epigastric fullness, weight loss, anemia, dysphagia, dyspepsia with abdominal tenderness and epigastric mass on physical examination [4,10]. Because most cases occur along the greater curvature of the stomach, the cysts can potentially compress the adjacent organs such as pancreas, kidney, spleen, and adrenal gland. Accordingly, the differential diagnosis would include lesions arising from these organs [2]. The cysts may also be manifested by complications such as infection, gastrointestinal bleeding, perforation, ulceration, fistula formation, obstruction, compression, or carcinoma arising in the cysts [7, 8]. Up to 10% of gastric duplications may contain ectopic pancreatic tissue which may lead to pancreatitis and mimic a pancreatic pseudocyst [3, 8].

Because of the rarity of adult gastric duplications, it is difficult to outline their natural history with certainty.

As with the native gastric mucosa, the cyst lining may undergo erosions, ulceration, and regenerative changes. In noncommunicating cysts, increased fluid production may result in pressure-induced necrosis of the mucosa. These changes may lead to bleeding into the cyst or perforation into the peritoneal cavity.

Duplication cysts have the potential for neoplastic transformation. The production of oncofetal antigens raises the problem of a precancerous condition in long standing intestinal duplications [8]. Out of 11 reported cases of malignancy arising within the duplication cysts, 8 were adenocarcinomas [4]. Five of the carcinomas originated from gastric duplications. Adenomyoma arising from a gastric duplication has also been reported [4]. Malignancies arising from duplication cysts are likely to be present at advanced stages because of their unusual symptoms and difficulty of diagnosis [4].

Although it is difficult to diagnose GDC preoperatively, recent imaging modalities have provided some informative findings. CT scan and endoscopic ultrasound (EUS) are the best ways to identify GDC [8]. Classically, radiographic studies show an intramural filling defect indenting the gastric contour [8]. Contrast-enhanced CT scan typically demonstrates GDC as a thick-walled cystic lesion with enhancement of the inner lining [2]. Calcification is occasionally observed on CT. These findings are of diagnostic significance for GDCs [2]. However, since mucinous cystic tumors of the pancreas also show similar radiological features, GDCs adjoining the pancreas are indistinguishable from pancreatic mucinous cystic tumors based on these CT findings. Moreover, because the wall is sometimes thin, enhancement of the inner cyst wall is not always demonstrated. Generally, MRI can provide additional information about the cyst content compared to CT scan. However, the nature of the fluid in the GDC was reported to differ in each case according to bleeding, chronic inflammation, or infection. Therefore, MRI seems to be of less significance than expected in diagnosing GDCs [2].

EUS is useful in distinguishing between the intramural and extramural lesions of the stomach. When EUS demonstrates a cyst with an echogenic internal mucosal layer and a hypoechoic intermediate muscular layer, the diagnosis of GDC is highly likely[2]. The role of EUS-guided FNA in GDC is uncertain because (a) the cytological features of GDC may closely resemble those of mucinous pancreatic neoplasms, and (b) GDCs with elevated levels of CEA and CA19-9 have been reported, mimicking mucinous pancreatic neoplasms [4, 8, 11].

Complete removal is the treatment choice to avoid the risk of possible complications such as obstruction, torsion, perforation, hemorrhage, and malignancy [9, 10]. A noncommunicating GDC is classically treated by complete excision of the cyst and resection of the shared wall between stomach and the duplication cyst [8]. Communicating GDC usually requires no intervention when both gastric lumens are patent [8]. Drainage and marsupialization of the cyst have been suggested. However, marsupialization into the stomach exposes the unprotected mucosa of the cyst to gastric contents with the risk of ulceration [4]. Drainage procedures such as cystojejunostomy may be complicated by stenosis of the anastomosis or blind loop syndrome and therefore discouraged [4]. Furthermore, leaving the cyst in place is ill-advised given the potential for malignant transformation [4].


Conclusion

In summary, this unusual developmental anomaly should be included in the differential diagnosis of cystic masses of the gastrointestinal tract, and the possibility of malignancy should also be considered. While the diagnosis of gastrointestinal tract duplications may be suggested by imaging studies, more often the correct diagnosis is not established prior to surgery. Due to the risk of malignant transformation and other complications, GDCs should be treated surgically by complete resection.




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