Fetus in fetu is a rare pathological condition, presenting as a congen
ital tumor. It consists of a malformed parasitic twin that is found wi
thin the body of its sibling, Less than 70 cases have been reported an
d in most of them a definite diagnosis was only made during surgery. W
e present a case with two fetuses in the retroperitoneum and describe
the criteria to be kept in mind for a correct preoperative diagnosis,
using the current imaging modalities.