The Disappearing Abdominal Mass: Mesenteric Pseudocyst

INTRODUCTION: Mesenteric pseudocyst is a term used to describe an abdominal cystic mass with an unknown abdominal origin. They are rare intra-abdominal masses, with a reported incidence of approximately 1 per 100,000 to 250,000 hospital admissions. Most cysts are benign and they may present differently, such as a disappearing mass or a mass that changes locations, thus posing a diagnostic challenge to the clinician. CASE REPORT: We describe a case of a 29-year-old woman who presented with a 2-year history of feeling a large mass within her abdomen, which would then disappear for several days and would frequently change position and be felt in different quadrants of her abdomen. Computed tomography scan of the abdomen revealed a large cystic structure, and a computed tomography–guided biopsy was inconclusive. Diagnostic laparoscopic surgery revealed a firm mass arising from the jejunal mesentery; the patient underwent an en bloc resection. Histopathologic examination of the resected mass revealed a rare diagnosis of mesenteric pseudocyst. Mesenteric pseudocyst should be should be kept high on the list of differential diagnoses when a patient presents with a disappearing mass and/or an abdominal mass that changes location.