Fetus– in –Fetu: CT Appearances

Fetus in Fetu (FIF) is a form of monozygotic diamniotic twin pregnancy where the parasitic twin installs and grows in the body of its partner.It shows calcification in majority of cases and is distinguished by its embryological origin, its unusual location in the retroperitoneal space with presence of vertebral organization and limb buds.This condition is a rare malformation that has some similarity with the retroperitoneal teratoma, but it is different from the latter by its fetiform aspect and the metameric segmentation of its spinal axis. The presence of a capsule covering this formation and a vascular pedicle is frequently encountered