Abdominal mass secondary to fetus-in-fetu in a neonate: case report and literature review

BACKGROUND: Among the various etiologies related to the presence of abdominal masses in newborns, the diagnosis of fetus in fetu (FIF), a term used to describe a congenital condition in which one fetus parasitizes the body, should be considered. Clinical case: We present the case of a male newborn who was found to have an abdominal mass during perinatal evaluation, leading to termination of pregnancy by cesarean section. After a thorough evaluation, a protocol was established that resulted in surgical intervention and the diagnosis of FIF. CONCLUSIONS: FIF is an exceptionally rare entity characterized by the presence of a "parasitic twin." Its pathophysiology and risk factors remain poorly understood, but it must be considered in the differential diagnosis of neonatal abdominal masses. Owing to its rarity, standardized follow-up protocols have not been established. Nevertheless, with current advances in pediatric surgery, the prognosis after complete excision is favorable.