We report a case of mesenteric chylous cyst diagnosed preoperatively b
y ultrasonography (US) and computed tomography (CT). Both demonstrated
a unilocular cystic mass with a fluid-fluid level, The CT number of t
he two components indicated fat density and water density and with sha
king or positional changes, the contents displayed miscibility. The tu
mor changed its position during hospitalization. Both features are con
sidered to be quite diagnostic of this condition.