A six-year-old patient consulted for periumbilical abdominal pain of 12 hours' duration accompanied by vomiting and a liquid stool. She presented with a low-grade fever, intense skin pallor and general malaise. Examination revealed a distended abdomen that was painful on palpation, with more intense defence in the right iliac fossa.
Suspicion of acute appendicitis led to a normal haemogram and emergency biochemistry. The abdominal X-ray showed marked dilatation of the small bowel loops in the left hemiabdomen and scant right gas, findings compatible with reflex ileus. Ultrasound showed great distension of the right colic frame with liquid content that displaced the rest of the small bowel loops to the left and the presence of a small amount of free liquid in the interassoid and Morrison's space, in relation to probable intestinal under-occlusion or occlusion, although the possible cause could not be determined.

Laparotomy revealed the presence of a large ileal lymphatic malformation occupying practically the entire abdominal cavity, multiple moderate-sized cysts (5 cm in diameter) and a larger cyst (15-20 cm in diameter). The loops of the ileum adjacent to the malformation show some degree of volvulus and moderate ischaemic involvement that completely reverses after devolvulation. Ileal resection is performed, completely including the malformation, with end-to-end anastomosis.
The pathological anatomy confirms the diagnosis of mesenteric cystic lymphangioma with a cystic mass of approximately 17 cm in diameter, with a smooth external surface and a vascular pattern on the wall corresponding to a single, multiseptate cavity filled with a slightly thick, cloudy yellow liquid. The wall is smooth internally and of a maximum thickness of 0.1 cm.