Huge omental lymphangioma with haemorrhage in children: case report.

Omental cystic lymphangioma is a rare benign intraabdominal anomaly with uncertain etiology, predominantly occurring in children. Most cases of abdominal lymphangioma are asymptomatic. However, patients may occasionally present with acute abdomen because of an intestinal obstruction or peritonitis caused by infected cysts, hemorrhaging, and/or torsion. This report describes a case of omental cystic lymphangioma with acute intracystic haemorrhage. Ultrasonography and computed tomography (CT) scan confirmed the diagnosis. Complete excision of the cyst along without omentectomy done with no clinical or radiological evidence of recurrence till 17 months.


Introduction
A lymphangioma is a benign proliferation of lymph vessels, producing fluid-filled cysts that result from a blockage of the lymphatic system.
Lamphangioma is located preferentially in head, neck, and axilla in children. However, lymphangiomas in abdomen are extremely rare.
From 50% to 60% of cystic lymphangioma cases present symptoms by age 1 year and 90% of the cases present by age 2 years [3].
Cases of abdominal lymphangioma present acute abdomen; attributed to intestinal obstruction [1] with volvulus [6], extrinsic compression and entrapment or peritonitis caused by rupture [7], torsion, haemorrhage into the cyst [8] or an infected cyst. Complete resection is the treatment of choice and has an excellent prognosis. Although an abdominal lymphangioma is considered benign, it may become locally invasive. Therefore, any involved organ must also be resected.
Incomplete resection may lead to recurrence. Follow-up imaging is advised, with ultrasound as the modality of choice.

Discussion
Lymphangioma is a benign lesion, with more than 80% of cases occurring during childhood [9,10]. It usually occurs in the head, neck, and axilla. Intraabdominal lymphangioma is very rare and comprises less than 5% of all lymphangiomas. From 50% to 60% of cystic lymphangioma cases present symptoms by age 1 year and 90% of the cases present by age 2 years [3]. The aetiology of lymphangioma is poorly understood but is generally believed to be a developmental abnormality associated with failure of the developing lymphatic tissues to establish normal communication with regional lymphatic drainage, resulting in dilatation of the abnormal channels [11]. Clinical presentation [12] may be chronic in which there is gradual distention in abdomen with or without pain. It may present in acute form in which there is acute pain, distention, fever, vomiting and peritonitis.
There may be features of small bowel obstruction which may occur by extrinsic luminal compression, by traction on the mesentery or by volvulus.
Plain radiographs may show a non-calcified soft-tissue mass, displacement of intestinal loops, or features of small bowel obstruction [13]. A well-circumscribed anechoic mass with posterior acoustic enhancement is a typical ultrasound presentation [14].
Computed tomography scan shows well defined, thin walled multiseptate lesion and distinguished from ascites by the absence of bowel loop separation or fluid in the typical sites, such as the cul-desac [15]. The cyst wall and septa can show enhancement after intravenous injection of contrast agent. Calcification is uncommon [11]. On magnetic resonance imaging, lymphangiomas have a low signal intensity on T1-weighted images and a high signal Page number not for citation purposes 3 intensity on T2-weighted images. If haemorrhage or infection occurs, the CT attenuation and magnetic resonance imaging signal pattern may alter [11]. Complications are intestinal obstruction (most common), volvulus, haemorrhage into the cyst, infection, rupture, cystic torsion and obstruction of the urinary and biliary tract [2].
Abdominal lymphangiomas should be differentiated from other abdominal cystic masses such as cystic teratomas, mucinous cystadenomas, bronchogenic cysts, ovarian cysts, nonpancreatic pseudocysts, and complicated ascites [3,16]. The presence of septa, compression on adjacent intestinal loops and lack of fluid in a dependent recess of the peritoneum and between leaves of the smallbowel mesentery suggests lymphangioma [15]. Complete resection with negative microscopic margins is the treatment of choice, even when asymptomatic, and any involved organ must also be resected [17]. Radical resection is sometimes technically impossible, because of local invasiveness with infiltration of adjacent organs or the main arterial branches. Incomplete resection has a 10% postoperative recurrence rate. Simple aspiration with or without injection of a sclerosing agent should be avoided because of extremely high risk of infection or recurrence rates [18]. If cysts are discovered prenatally, intervention during early infancy is indicated to prevent potential complications such as obstruction and intestinal volvulus.
Laparoscopic resection is an excellent alternative to conventional open abdominal resection, and gives the patients the advantages of minimally invasive surgery [19]. In our patient the cyst was found in the greater omentum which was excised completely without omentectomy or bowel resection. Follow-up imaging is advised, with ultrasound as the modality of choice.

Conclusion
In a case of large cystic mass with thin walls, internal echogenicities and septations, the diagnosis of omental lymphangioma should be suspected, but histological diagnosis is necessary for definitive diagnosis. This rare case is presented because of its unusual presentation with huge size and acute intracystic haemorrhage.

Competing interests
The authors declare no competing interests.

Authors' contributions
All the authors contributed to the writing of the paper. All authors read and approved the final manuscript.