Eight months old boy was brought by his mother with complaints of progressive increase in size of the abdomen since one week. He had not passed stools since three days. He had no history of melena, jaundice, vomiting or fever. There was no loss of weight or appetite in the past. His birth history was normal. Routine blood investigations were unremarkable.
On ultrasound examination of the abdomen, a large well-defined cystic lesion of size 17.5x14x7.5 cm was seen occupying the entire abdomen and pelvis. There were multiple thin, smooth septations within it. The bowel loops were displaced laterally and posteriorly by the above lesion. Due to the unavailability of MRI, the child was subjected to a contrast-enhanced computed tomography (CT) of the abdomen and pelvis for further evaluation of the mass lesion, which confirmed the above findings. There was mass effect on the stomach and the bowel loops. There were no calcifications in the wall of the lesion or along its septations. There were no solid enhancing components. There were no focal lesions in the liver or spleen. Rest of the abdominal organs appeared normal. There was no free fluid.
A presumptive diagnosis of lymphangioma was made. The diagnosis was confirmed on surgery. On excision of the specimen, milky fluid representing chyle oozed out from a few of the cysts, while the others revealed serosanguinous fluid. Histopathological examination showed large cyst-like vascular spaces lined by flattened epithelium, the walls of which showed fibro cartilaginous tissue, lymphatic channels and lymphocytes, consistent with a lymphangioma.
Lymphangiomas are congenital vascular malformations which usually occur in the neck, axilla and abdomen. In the abdomen, they can arise from mesentery, omentum, gastrointestinal tract or retroperitoneum. Separation of lymphatic channels from the normal network of lymph vessels during development may lead to lymphatic malformations. Congenital lymphangiomas are formed due to blockade of the lymphatic system during fetal development. In the absence of venous drainage, they progressively accumulate fluid.. They are most commonly found in children and the clinical presentation includes abdominal pain, distension, palpable mass, nausea, vomiting, constipation and diarrhea. The associated complications may be torsion, hemorrhage, infection, rupture and intestinal obstruction.
Ultrasonography is a useful, non-invasive initial modality of investigation. It has been shown to be superior to CT in the demonstration of the composition of these lesions.  On all modalities, lymphangiomas present as cystic lesions which may have internal echoes and septae. Capsular enhancement may be seen on CT. Hemorrhage or infection can lead to higher attenuation values. MRI is useful in determining extension, especially in deeper locations such as mediastinum, thorax and retroperitoneum.  It is the preferred modality, as it avoids the use of ionizing radiation in the pediatric age group. The use of CT in this case, is a limitation of this study, due to the non-availability of MRI at that time.. Nodularity or thick enhancement of septations could suggest alternative diagnosis.  The other differential diagnosis for ‘mesenteric cysts’ include enteric duplication cysts, non pancreatic pseudo cysts and mesothelial cysts. Meconium cysts can be found in the perinatal period. Wall calcifications, intraluminal air and a dilated bowel loop communicating with the lesion can point towards the diagnosis. Cystic teratomas usually have ectodermal derivatives such as teeth, hair, fat and calcification within them. Duplication cysts may be adherent to a bowel loop and characteristically show a ‘double wall’ with inner echogenic mucosa and surrounding hypoechoic rim.  Abscesses show thick enhancing wall with internal debris and surrounding inflammatory changes. A clinical history of prior surgery, trauma or infection may be present. Ovarian cysts have to be considered in females. Very rarely, a mesenchymal hamartoma may present as a septated, cystic lesion in the abdomen of a neonate. A cystic neuroblastoma is an uncommon cause of an abdominal mass in children; calcifications are present in majority of the cases.
Malignant conversion of a lymphangioma to lymphangiosarcoma is rare.  Treatment of choice is complete surgical excision. Sclerotherapy is a less invasive form of treatment. Rate of recurrence depends on the location, size and complexity of the lesion.
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