Giant retroperitoneal fetus-in-fetu: An unusual cause of respiratory distress

Fetus-in-fetu (FIF) is a rare congenital condition in which a vertebrate fetus is incorporated within its host, a newborn or an infant. We report an interesting case of FIF presenting as an abdominal mass with respiratory distress in a 4-month-old girl, and review the existing literature. An ultrasound abdomen showed a right sided cystic mass containing multiple calcifications. Laparotomy revealed a well-encapsulated right retroperitoneal mass above the right kidney with two rudimentary limbs attached to an amniotic bag by an umbilical cord. Excision of the capsule revealed a yellowish fluid and an incompletely developed fetus covered by vernix caseosa. Pathologic examination showed an irregular fetiforme mass, weighing 1200 gm, with two rudimentary limbs, encephalus, stomach, duodenum, bowel, bone, cartilage, bone marrow, upper and lower respiratory tissue, and spleen. Complete excision of the FIF was performed. The postoperative period was uneventful and the patient was discharged on the seventh postoperative day.