A Case of A Mesenteric Cyst Mimicking a Biloma.

Mesenteric cysts are a rare entity, with approximately 1,000 cases reported in the literature. Its etiology is unknown but was theorized to be a benign ectopic lymphatic proliferation in the mesentery. Imaging with surgical excision and pathologic microscopic evaluation is needed for diagnosis, but no specific guidelines for its management have been documented. Per most cases in the literature, drainage of mesenteric cysts is suboptimal and associated with increased risk of recurrence and infection, making surgical resection the treatment of choice. With its varying locations and presentations, diagnosis can be tricky especially given the rarity of its occurrence. Differential diagnosis includes pancreatic pseudocyst, hemangioma, choledochal cyst, hydatid cyst, cystic teratoma, etc. We present a 35-year-old woman who came in with worsening right upper quadrant (RUQ) pain due to chronic cholelithiasis and was found to have a large RUQ cystic mass adherent to the gallbladder, suggesting possible biloma or pancreatic pseudocyst; however, tissue analysis was positive for a mesenteric cyst.