Male infant aged one month, with no personal history of interest, who came to the emergency department for the third time in the last week with a partially consolable crying episode. He had been diagnosed with infant colic and the usual measures were recommended. He is exclusively breastfed. In the last 48 hours his feeding has been worse, his crying, which was initially in the evening, has continued all day and the mother has not been able to calm him in her arms since yesterday. He remains afebrile and in excellent general condition, with adequate weight gain, currently weighing 4 kg. Physical examination reveals abdominal distension and palpation of a periumbilical mass extending to the right flank, with no obvious defence. She frankly refused breastfeeding in the emergency department and presented with vomiting of food.
With suspicion of intestinal obstruction, an abdominal X-ray showed marked abdominal silence (absence of gas) in the right hemiabdomen and a mass effect with displacement of the intestinal loops towards the left hemiabdomen. The ultrasound scan showed a central abdominal image measuring approximately 9 x 8.7 x 7.9 cm, which appeared as a large space-occupying focal lesion with cystic characteristics and no vascular flow on colour Doppler and multiloculated and multitabulated.

The patient was transferred to a reference centre for paediatric surgery. The study was completed with magnetic resonance imaging (MRI) of the abdomen, which revealed a voluminous intra-abdominal cystic mass measuring 90 x 60 x 65 mm, located mainly in the right flank and the central abdominal region. It extends from the lower edge of the liver, in front of the right kidney, displacing the intestinal structures to the left. It is a multilocular mass with well-defined borders and thin walls, with multiple cystic components of different sizes. The first suspected diagnosis was cystic lymphangioma of the mesentery.

The patient underwent mid laparotomy and a multicystic mass containing whitish liquid was excised from the mesentery of a loop of the middle ileum. The loop was resected and end-to-end anastomosis was performed. The postoperative period, the first 24 hours in the Paediatric Intensive Care Unit (PICU) and the rest on the ward, was uneventful and in eight days the patient was sent home with adequate enteral tolerance and no complications.
The pathological anatomy confirms the diagnosis of mesenteric cystic lymphagioma with a multiseptate cystic mass of approximately 5 cm in diameter with a smooth whitish wall and a thickness of 0.1 cm.