Gangopadhyay et al. Journal of Medical Case Reports 2010, 4:96 http://www.jmedicalcasereports.com/content/4/1/96 C A S E R E P O R T JOURNAL OF MEDICAL CASE REPORTS Open Access Twin fetus in fetu in a child: a case report and review of the literature Ajay N Gangopadhyay1*, Arvind Srivastava2, Punit Srivastava1, Dinesh K Gupta1, Shiv P Sharma1, Vijayendra Kumar1 Abstract Introduction: Fetus in fetu is an extremely rare condition wherein a malformed fetus is found in the abdomen of its twin. This entity is differentiated from teratoma by its embryological origin, its unusual location in the retroperitoneal space, and the presence of vertebral organization with limb buds and well-developed organ systems. The literature cites less than 100 cases worldwide of twin fetus in fetu. Case presentation: A two-and-a-half-month-old Asian Indian baby boy had two malformed fetuses in his abdomen. The pre-operative diagnosis was made by performing an ultrasound and a 64-slice computer tomography scan of the baby’s abdomen. Two fetoid-like masses were successfully excised from the retroperitoneal area of his abdomen. A macroscopic examination, an X-ray of the specimen after operation, and the histological features observed were suggestive of twin fetus in fetu. Conclusion: Fetus in fetu is an extremely rare condition. Before any operation is carried out on a patient, imaging studies should first be conducted to differentiate this condition from teratoma. Surgical excision is a curative procedure, and a macroscopic examination of the sac should be done after twin or multiple fetus in fetu are excised. Introduction Fetus in fetu (FIF) is a rare condition associated with abnormal embryogenesis in a diamniotic, monochorionic pregnancy, wherein a vertebrate fetus is enclosed within the body of another normally developing fetus [1]. The FIF complex is characteristically composed of a fibrous membrane (equivalent to the chorioamniotic complex) that contains some fluids (equivalent to the amniotic fluid) and a fetus suspended by a cord or pedicle. In the uterus, the growth of an FIF initially parallels that of its twin, but stops abruptly because of either the vascular dominance of the host twin or an inherent defect in the parasitic twin [2]. FIF is mostly anencephalic, but in almost all cases its vertebral column and limbs are pre- sent (91% and 82.5%, respectively). At the same time its lower limbs are more developed than the upper limbs. An FIF is rarely found in the central nervous system, gastrointestinal tract, retroperitoneum, vessels or geni- tourinary tract of its host twin. It is found even more rarely in the lungs, adrenal glands, pancreas, spleen or * Correspondence: gangulybhu@rediffmail.com 1Department of Pediatric Surgery, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India lymph nodes [3]. Even without performing an operation to remove the parasitic twin, the existence of the condi- tion can be diagnosed through ultrasonography, plain X-ray and a computed tomography (CT) scan of the host’s abdomen. The surgical removal of the twin fetus is the treatment of choice. In most cases of FIF, only one fetus exists inside the baby. Only in extremely rare cases are multiple fetuses found. Case presentation A two-and-a-half-month-old, first-born, Asian Indian baby boy was admitted to the department of Pediatric surgery, S.S hospital, BHU, due to recurrent episodes of vomiting and abdominal distension since he was one month old. Upon examination of the baby’s abdomen we discovered that a smooth, firm and non-tender mass was present in the left half of his abdomen. Conven- tional X-ray of the abdomen showed a soft tissue mass with a vertebrae-like column (Figure 1). An ultrasound of the baby’s abdomen showed a large, encysted, hypere- choic and calcified heterogenous complex mass. A 64- slice CT scan of his abdomen revealed a soft tissue mass © 2010 Gangopadhyay et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.