A Case of Mesenteric Pseudocyst Causing Massive Abdominal Swelling

We present the case of a 55-year-old man with a self-limiting febrile condition associated with polyserositis with an inconclusive investigation. Bilateral pleural and pericardial effusions resolved. The peritoneal fluid loculated and was compatible with an exudate. The patient remained clinically asymptomatic. However, 2 years later, examination revealed a palpable and painless abdominal mass, which imaging suggested a cystic lesion. Surgical resection was performed and histological examination identified a mesenteric pseudocyst. Mesenteric pseudocysts are rare intra-abdominal cystic masses which are mostly benign and do not cause specific symptoms. Although imaging tests are useful for their differential diagnosis, histology is mandatory. LEARNING POINTS: Mesenteric pseudocysts are rare intra-abdominal cystic masses with a clinical presentation that sometimes is a diagnostic challenge. Abdominal imaging used to investigate a concomitant systemic illness may reveal a fluid lesion which may delay the diagnosis. Ultrasound, computed tomography and magnetic resonance imaging can be used for pre-operative diagnosis, but exact differentiation is only achieved through histopathological examination.