Fetus in Fetu: A Rare presentation in an Adult female

Anesthetic Care During Exploratory Laparotomy and Excision of a Fetus-in-Fetu With a Combined General-Regional Anesthetic Technique Using a Caudal Epidural Catheter

Fetus-in-fetu (FIF) is a rare, congenital anomaly involving the presence of one of a pair of twins within the body of the other. It is postulated that this pathology occurs during embryogenesis of a diamniotic-monochorionic twin pregnancy with unequal division of the blastocele, which results in monozygotic, monochorionic, and diamniotic twins of unequal sizes. Presentation as an abdominal mass during the neonatal period or infancy is most common, although late diagnosis during the adult years may also occur. We report a 1-day-old, full-term female neonate who presented for exploratory laparotomy and excision of a FIF. We present the use of a combined general-regional technique using caudal epidural anesthesia. The etiology, presentation, appropriate workup, and treatment of FIF are presented. Previous anecdotal reports of anesthetic care for excision of FIF are reviewed.

Fetus in Fetu: Case Report and Brief Review of Literature on Embryologic Origin, Clinical Presentation, Imaging and Differential Diagnosis

BACKGROUND

Fetus in fetu (FIF) is a rare entity in which a malformed diamniotic monochorionic parasitic fetal twin develops inside a normal co-twin's body, most commonly in the abdominal cavity. FIF is differentiated from the teratoma by the presence of vertebral column often with an appropriate arrangement of other organs or limbs around it.

CASE REPORT

A two-and-a-half-year-old girl presented with a painless abdominal swelling in the right hypochondrium. On imaging, a heterogenous soft tissue mass with internal calcific densities was noted in the retroperitoneum. The mass had vertebral organization, limb and pelvic bones. The presence of a fetiform teratoma was suspected and surgery revealed an encapsulated mass with an anencephalic head, spine, upper and lower limb buds. Histopathology confirmed the presence of a fetus in fetu. The postoperative period was uneventful with no evidence of recurrence.

CONCLUSIONS

FIF is a pediatric rarity. Cross-sectional imaging helps in differentiating it from a teratoma, meconium peritonitis and abdominal ectopic pregnancy. Surgical excision is the treatment of choice for this benign condition, which requires a follow-up only in certain cases. This case report describes a retroperitoneal fetus in fetu and discusses its clinical presentation, differential diagnosis and embryologic origin.