Case Report: Prenatal Diagnosis of Fetus in Fetu: A Review of the Japanese Literature

Abstract

Fetus in fetu is a rare abnormality in which a deformed fetus is absorbed into another fetus. Its pathogenic mechanism is different from that of teratoma, but its differential diagnosis is important. The majority of such cases are found from the neonatal period to infancy. Ultrasonography shows the characteristic signs of a solid mass with bony structures within a fluid-filled sac. Prenatal or preoperative diagnosis would be helpful. MRI or CT shows the vertebrae, feeding artery or location of the mass, and on the basis of such findings, we can determine the operative period and operative approach. We report the prenatal diagnosis of fetus in fetu by ultrasonography, which showed highly differentiated organs. Because the mass had been increasing after birth and the patient could not suckle, we performed the operation in the early neonatal period.