A Case of Foetus-in-Fetu

Background: A foetus-in-fetu (FIF) is a very rare congenital abnormality (incidence of 1 in 5.00,000 live births) in which a mass of tissue, a malformed foetus grows within the body of the foetus. It is an unusual cause of the abdominal mass in neonates. We here report a case of FIF in a newborn male for its rarity and interest in its evolution. Case report: A one-day-old male term neonate was referred for evaluation of abdominal mass. Antenatal ultrasonogram at 32 weeks of gestational age revealed a complex multi-septated cystic lesion with internal echogenic components. Clinical examination revealed a distended abdomen with an ill-defined mass filling the entire abdominal cavity. Plain X-ray abdomen revealed a mass on the right side of the abdomen with few long bone-like densities and few vertebrae. An ultrasonogram showed ill-defined hetero echoic lesions, measuring 10.9 × 11.1 Centimeters, with solid and cystic components and few calcifications in the mass. The CT scan of the abdomen showed an ill-defined mass lesion on the right side of the abdomen, measuring 11.3 × 6.6 × 9.9 Centimeters, with internal soft tissue, distorted long bones, and few vertebrae in the subhepatic region of the right hypochondrium. The 3-dimensional reconstruction of the CT scan confirmed the diagnosis of FIF. On laparotomy, the mass had a covering membrane attached to the adjacent abdominal wall and was connected by a cord-like structure with vessels. Excision of the mass was done in toto and the post-operative period was uneventful. Conclusion: FIF is considered a benign condition that causes mass effects on the adjoining organs and should be considered a differential diagnosis in neonates with abdominal distension.