Mesenteric and Omental Cysts in Children

Mesenteric and omental cysts can be either simple or multiple and either unilocular or multilocular, and they may contain hemorrhagic, serous, chylous, or infected fluid.[8] The fluid is serous in ileal and colonic cysts and is chylous in jejunal cysts.[9, 10] They can range in size from a few millimeters to 40 cm in diameter. (See the images below.)

As proposed by Gross, mesenteric and omental cysts are thought to represent benign proliferations of ectopic lymphatics that lack communication with the normal lymphatic system.[11, 12, 13] Cysts are thought to arise from lymphatic spaces associated with the embryonic retroperitoneal lymph sac; this makes them analogous to cystic hygromas, which arise in the neck in association with the jugular lymph sac.[14]

Another proposed etiology is lymphatic obstruction[5] ; however, experimental occlusion of lymphatic channels in animals does not produce mesenteric or omental cysts because of the rich collaterals in the lymphatic system, a finding that has shed doubt on this particular theory.[15, 12, 14] Other etiologic theories include the following[8] :

• Failure of the embryonic lymph channels to join the venous system
• Failure of the leaves of the mesentery to fuse
• Trauma
• Neoplasia
• Degeneration of lymph nodes

Another variation includes chylous mesenteric cysts, which have a slight male to female preponderance of 1.4:1; presentation is usually in the fourth decade of life.[16] Primary mesenteric hydatid cysts have also been reported; these are extremely rare and present with chronic lower abdominal pain.[17]

Mesenteric cysts have been reported in association with Costello syndrome, which consists of short stature, redundant skin of the neck, palms, soles, and fingers, curly hair, papillomata around the mouth and nares, and mental retardation.[18]

Mesenteric cysts can occur anywhere in the mesentery of the gastrointestinal (GI) tract from the duodenum to the rectum, and they may extend from the base of the mesentery into the retroperitoneum.[8, 15] In a series of 162 patients, 60% of mesenteric cysts occurred in the small-bowel mesentery, 24% in the large-bowel mesentery, and 14.5% in the retroperitoneum. They most commonly occur in the ileal mesentery of the small bowel or the sigmoid mesentery of the colon.[19]

Omental cysts are confined to the lesser or greater omentum.[6] Congenital omental cysts that present as abdominal distention have been reported.[20] Omental cysts may be a result of dermoid cysts[21] or teratomas.[22]

Mesenteric and omental cysts are rare; the incidence is about 1 per 140,000 general hospital admissions and about 1 per 20,000 pediatric hospital admissions.[19, 15, 9] In a study from Egleston Children's Hospital at Emory University from 1965 to 1994, 14 patients were treated for mesenteric or omental cysts, which represents a prevalence of about 1 case per 11,250 admissions.[8]

Approximately one third of cases occur in children younger than 15 years.[11, 23, 10] The mean age of children affected is 4.9 years.[11, 10, 24, 6, 25, 26, 27] Mesenteric cysts are 4.5 times more common than omental cysts.[28]

Overall results in pediatric patients are favorable. The recurrence rate ranges from 0% to 13.6%,[11, 10, 25, 26, 28] averaging about 6.1% in a series of 162 adults and children.[19] Most recurrences occur in patients with retroperitoneal cysts or those who had only a partial excision.[19, 25, 26, 28]

Essentially no mortality is associated with mesenteric or omental cysts in children; only one pediatric death has been reported since 1950.[29] In a series from Egleston Children's Hospital in Atlanta, no major postoperative complications, recurrences, or deaths occurred.[8]

A mesenteric or omental cyst may be discovered as an incidental finding during laparotomy for another condition or during diagnostic imaging,[30] or it may manifest as an acute life-threatening intra-abdominal catastrophe.[6]

Children generally present with abdominal distention and few associated symptoms other than vague abdominal pain with or without a palpable mass.[5, 31, 32] The mass may be huge, simulating ascites.[33, 34] The most common mode of acute presentation in children is that of a small-bowel obstruction, which may be associated with intestinal volvulus or infarction.[10, 6, 26, 35]

Approximately 10% of patients with mesenteric and omental cysts present with an acute abdominal emergency.[6] These masses can be detected with antenatal ultrasonography (US) and appear as a sonolucent mass. The antenatal differential diagnosis includes the following:

• Dilated bowel (eg, intestinal atresia)
• Dilated stomach (eg, pyloric atresia)
• Gastrointestinal duplication
• Hydronephrosis
• Ovarian cyst
• Cystic teratoma

In a series of 82 children who underwent surgery for various causes of intestinal volvulus, mesenteric cysts were the underlying etiology in 3.65% of cases.[36]

A very unusual presentation of a mesenteric cyst is that of an irreducible inguinal hernia.[1] The differential diagnosis includes the following[6] :

• Intestinal duplication cyst
• Ovarian, choledochal, pancreatic, splenic, or renal cysts
• Hydronephrosis
• Cystic teratoma
• Hydatid cyst
• Ascites

An extragastrointestinal stromal tumor presenting as an omental cyst was described in a case report by Monabati et al.[37]  A congenital giant omental hemorrhagic cyst presenting as acute hemorrhagic anemia in an infant was described in a case report by Kokhanovsky et al.[38]

Various complications have been associated with mesenteric and omental cysts, including the following[6] :

• Intestinal obstruction (most common)
• Volvulus
• Hemorrhage into the cyst
• Infection
• Rupture
• Cystic torsion
• Obstruction of the urinary and biliary tract

Malignant transformation of mesenteric cysts has occurred in adults,[19] but malignant mesenteric and omental cysts have not been reported in children.[6]

No specific laboratory studies aid in the diagnosis of mesenteric and omental cysts. Aside from imaging studies (see below), no tests or diagnostic procedures are necessary.

Radiography

Plain abdominal radiography may reveal a gasless, homogeneous, water-dense mass that displaces bowel loops laterally or anteriorly in the presence of a mesenteric cyst or posteriorly in the presence of an omental cyst.[8, 5]  Fine calcifications can sometimes be observed within the cyst wall.[6, 39, 40]

Ultrasonography

The imaging modality of choice is abdominal ultrasonography (US).[10, 26, 27, 40] US reveals fluid-filled cystic structures, commonly with thin internal septa and sometimes with internal echoes from debris, hemorrhage, or infection.[11, 27, 40, 41] However, these can be confused with large ovarian cysts in the fetus and newborn.

Enteric duplication cysts, on the other hand, are thick-walled structures that share a common muscular wall with the adjacent bowel. They also have a clearly visible mucosal lining on US.

Other modalities

Abdominal computed tomography (CT) adds minimal additional information, though it can reveal that the cyst is not arising from another organ such as the kidney, pancreas, or ovary.[9]  Radionuclide scanning of the biliary tract excludes choledochal cysts from diagnostic consideration.[6] Contrast CT aided by angiography may be useful in cases of large omental cysts.[42]

Cystic lymphangiomas are sometimes differentiated from mesenteric and omental cysts.[15, 11, 26] Cystic lymphangiomas have an endothelial cell lining, foam cells, and thin walls that contain lymphatic spaces, lymphoid tissue, and smooth muscle; mesenteric cysts lack smooth muscle and lymphatic spaces, and the cells lining the cysts are cuboidal or columnar in nature.[15]

Lymphangiomas are more diffuse and occur in the mesentery or retroperitoneum, and patients may present earlier in life than those with mesenteric or omental cysts.[15, 26, 43] In a series of 191 patients with lymphangioma, 4.7% of patients presented with lymphangioma in the mesentery.[44]

For the purposes of this discussion, a mesenteric cyst is defined as any cyst that is located in the mesentery and may or may not extend into the retroperitoneum; a mesenteric cyst also has a recognizable lining of endothelial or mesothelial cells. An omental cyst has the same histologic characteristics but is confined to the greater or lesser omentum.[6]

No medical therapy is available. In children with mesenteric or omental cysts, the most common indication for surgical intervention is the presence of an abdominal mass with or without signs of intestinal obstruction.

With the widespread use of antenatal ultrasonography (US), mesenteric and omental cysts are being diagnosed in utero.[45, 6] No role for treating these cysts in utero is recognized. If cysts are discovered antenatally, intervention during early infancy is indicated to prevent potential complications such as obstruction and intestinal volvulus.[46]

The goal of surgical therapy for mesenteric and omental cysts is complete excision of the mass.[47] Omental cysts can be removed without endangering the adjacent bowel.[11, 6, 25]

Surgical options

The preferred treatment of mesenteric cysts is enucleation,[19, 9, 25, 5] though intestinal resection is frequently required to ensure that the remaining bowel is viable. Bowel resection may be required in 50-60% of children with mesenteric cysts, whereas resection is necessary in about one third of adults.[19, 11, 10, 6, 26] Any resulting mesenteric defect must be closed to prevent an internal hernia.

If enucleation or resection is not possible because of the size of the cyst or because of its location deep within the root of the mesentery, the third option is partial excision with marsupialization of the remaining cyst into the abdominal cavity.[6] Approximately 10% of patients require this form of therapy.[19] If marsupialization is performed, the cyst lining should be sclerosed with 10% glucose solution,[23] electrocautery, or tincture of iodine to minimize recurrence. Partial excision alone with or without drainage is not indicated, because of the high recurrence rate associated with these procedures.[19]

Laparoscopic management of mesenteric cysts is also being reported.[48, 49, 50, 51, 52] If necessary, depending on the expertise in laparoscopic surgery in children, laparoscopy could be used to localize the cysts, and resection could be performed through a small laparotomy or via an extended umbilical incision. Furthermore, reports suggest successful drainage and marsupialization of mesenterial cysts, which avoids enterotomy.[53] Management of mesenteric cysts by means of US-guided drainage has also reported to be successful.[54]

Preparation for surgery

The patient should undergo standard preoperative preparation for a major laparotomy. This includes inserting a nasogastric tube, initiating intravenous (IV) fluid therapy, and beginning prophylactic antibiotics preoperatively in the event that a bowel resection is required. If time allows, the patient should undergo mechanical bowel preparation for the same reason.

Operative details

Mesenteric cysts can be shelled out from between the leaves of the mesentery with fine electrocauterization, with care taken not to damage the blood vessels to the adjacent intestine. If this is not feasible, a standard bowel resection with a primary end-to-end anastomosis is performed. Intestinal diversion is not necessary unless gross peritonitis from a long-standing bowel perforation is present.

Omental cysts are excised by removing the involved portion of the mesentery up to the transverse colon if necessary. In the vast majority of cases, removing the adjacent colon or stomach is not necessary.[6, 25]

After operative treatment, the patient is maintained on NPO (nil per os) status with IV fluids and nasogastric suction until bowel function returns. Prophylactic antibiotics can be discontinued after one or two postoperative doses. If the patient is not able to eat by postoperative day 3, parenteral nutrition should be provided.

Complications from surgery, either early or late, are uncommon.[8]

Routine postoperative follow-up care 2-3 weeks after discharge from the hospital is indicated. The child's family should be warned about the potential for intestinal obstruction from adhesions. If the patient was treated with marsupialization, closer follow-up for possible recurrence should be instituted. Otherwise, long-term results for simple excision are favorable.[55]