Fetus-in-fetu.

INTRODUCTION: Fetus-in-fetu (FIF) is a pathological condition in which the malformed foetus is found in the body of its twin. We report this rare case of a 3-month-old female baby whose diagnostic work-up suggested a mesenteric cyst but the mass at surgery was a FIF. DISCUSSION: Although current imaging modalities like computerized Tomography and magnetic resonance imaging have a higher Sensitivity for accurate delineation of tissues, cheaper imaging alternatives like plain abdomen and ultrasonography still have a place in the preoperative work-up of FIF.