Teaching Case

A 35-year-old woman was admitted to the hospital’s emergency unit with acute abdominal pain. The woman had diffuse pain in the abdomen, started acutely the same day. She had a history without any previous diseases. She had visited Morocco the week before

At the CT images, we see a hypodense lesion to the left, and anteriorly and posteriorly we see parts of the descending colon and laterally a part of the ileum (fig 1). We see reactions in the fatty tissue, especially towards the lateral small intestines (fig 1 and 2). At CT it looks like inflammatory changes in the fatty tissue; this is not seen at the MRI (fig 3-6).  Combined information from the two modalities shows that the lesion is in the mesentery. MRI shows that it contains both fat and fluid. It is well delineated, but the CT indicates some reactive changes in the surrounding fat, especially towards the small intestine. Several small lymph nodes are present, best seen at CT (fig 2).

Background
This mesenteric cyst is rare and may appear anywhere in the mesentery of the gastrointestinal tract, and thus all cystic lesions both centrally in the abdomen and in the pelvis may be differential diagnoses. The literature is limited, with case reports that also include reviews of published case reports [1-3]. It was first described by von Rokitansky in 1842 [1, 3].

Clinical perspective
These patients may well be without any symptoms. These lesions are most commonly detected due to vague abdominal pain or incidental findings [1]. The treatment is either conservative, a complete resection or an enucleation, according to symptoms [1]. Such a mass may affect the bowels and cause obstruction or affect other organs and cause indirect symptoms. In this case, the patient’s symptoms were over after two days, and only conservative treatment was considered (do nothing, but come back if new symptoms).

Imaging perspective
The imaging perspective is the most interesting as the mass may mimic several other entities. The literature tells that pseudocysts of the pancreas, ovarian cysts, cystic tumours, aneurysms and dermoid cysts have all been differential diagnoses. In this case, the radiologist reporting the CT thought of inflammatory possibilities and had an abscess as first differential diagnosis but also mentioned dermoid cyst. The radiologist reporting the MRI, which showed a content of both fat and fluid, added dermoid tumour with fat, ecchinococcus cyst and liposarcoma to the list of differential diagnoses. Our sarcoma group negated liposarcoma, a consensus group of radiologists said that it looked benign and even mentioned the correct diagnosis as an option, concluding that this is some sort of benign cystic lesion in the mesentery. The final diagnosis was confirmed with fine needle aspiration for bacteriology and cytology.

Final diagnosis and patient outcome

This was diagnosed as a chylous mesenteric cyst. Both the group of radiologists and the multidisciplinary group suggested this, and it was confirmed.
The patient was discharged for home without any symptoms. Further control only with reappearing symptoms. The aetiology of chylous mesenteric cysts is unclear; a large part of them are probably genetic.

All patient data have been completely anonymized throughout the entire manuscript and related files.