Case report: rare congenital anomaly diagnosed by ultrasonography

Objectives: Report a rare congenital anomaly diagnosed by obstetric ultrasound. Methods: The pregnant woman suspected of have fetus with congenital anomaly was attended in the fetal medicine service of a public maternity hospital in Goiás, Brazil. A hyperechogenic nodule in the mesoabdomen of a male fetus were observed through ultrasonography. The totipotent cell mass was withdrawn one week postpartum. The anatomopathological analysis performed confirmed fetal tissue type FIF. Results: The ultrasonography performed at the institution detected the presence of a hyperechogenic nodule with 2cm shade in the mesoabdomen of a male fetus, performed at the 30th week of gestation. The totipotent cell mass was withdrawn during labor. It had bones and limbs under development. This pathology is due to abnormal embryogenesis. In these cases, a vertebrate fetus is enclosed within the body of another normally developed fetus and kept by a pedicle in an area filled with liquid or sebaceous material, with no placental or chorionic tissue. Intrauterine growth of FIF is initially similar to its twin, with its subsequent arrested development in a precipitate way due to the “host’s” vascular domain or an inherent defect of the “parasitic” twin. The entity is rare and interesting, typically presented in childhood or early childhood. Conclusions: Current imaging modalities, such as pre and postnatal ultrasonography, can accurately diagnose the condition. Complete excision is curative and allows confirmation of the diagnosis.