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Year : 2023  |  Volume : 28  |  Issue : 5  |  Page : 439-441

Fetus-in-fetu: A tale of the trapped triplets

1 Department of Pediatric Surgery, IMS-Banaras Hindu University, Varanasi, Uttar Pradesh, India
2 Department of Pathology, IMS-Banaras Hindu University, Varanasi, Uttar Pradesh, India
3 Department of Radiology, IMS-Banaras Hindu University, Varanasi, Uttar Pradesh, India

Date of Submission19-May-2023
Date of Decision05-Jun-2023
Date of Acceptance23-Jun-2023
Date of Web Publication05-Sep-2023

Correspondence Address:
Vaibhav Pandey
Department of Pediatric Surgery, Banaras Hindu University, Varanasi, Uttar Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiaps.jiaps_113_23

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A 7-day-old male child presented with abdominal distention and jaundice. Radiological investigations revealed an encapsulated sac encasing three fetus-in-fetu (FIF) in the retroperitoneum. Laparotomy revealed a sac occupying almost the whole of the abdomen. The sac was stretching the duodenum and barely visible common bile duct, which were carefully separated. The rest of the bowel was displaced to the left. The sac containing three FIFs was excised intact. One of the fetuses was highly differentiated and had thoracic meningomyelocele, which has never been reported in FIF.

Keywords: Fetus-in-fetu, meningomyelocele, obstructive jaundice

How to cite this article:
Nandan R, Kachhap S, Sengar P, Ghosh A, Pandey V, Indal M. Fetus-in-fetu: A tale of the trapped triplets. J Indian Assoc Pediatr Surg 2023;28:439-41

How to cite this URL:
Nandan R, Kachhap S, Sengar P, Ghosh A, Pandey V, Indal M. Fetus-in-fetu: A tale of the trapped triplets. J Indian Assoc Pediatr Surg [serial online] 2023 [cited 2023 Oct 2];28:439-41. Available from: https://www.jiaps.com/text.asp?2023/28/5/439/385139

   Introduction Top

Fetus-in-fetu (FIF) is a diamniotic, monochorionic, monozygotic malformed parasitic twin incorporated within the fellow twin's body during embryonic development.[1],[2] The etiology is controversial. It has been proposed to be caused by the persistent anastomosis of vitelline circulation.[2] While some propose that the totipotent inner cell mass of the developing blastocyst divides unequally, forming a small cell mass in maturing sister embryos.[1] A single FIF has been reported in 89% of case reports.[3] Less commonly, there may be multiple fetuses.[2] We hereby report a case where three FIFs were seen, which is rare.

   Case Report Top

A 3.3 kg male child was born at full term by normal vaginal delivery. He had abdominal distention at birth. He was noted to have jaundice on day 2 of life. It was associated with clay-colored stools. On day 7 of life, he was referred to our hospital. On examination, the child had icterus. The abdomen was distended with everted umbilicus and dilated veins. Approximately 15 cm × 10 cm firm mass was palpable, occupying the whole abdomen. The surface and margin were irregular.

X-ray abdomen was suggestive of three FIFs [Figure 1]a. On ultrasound abdomen, an encapsulated sac having three FIFs was seen. Contrast-enhanced computed tomography (CECT) abdomen showed a well-encapsulated sac in the anterior pararenal space, predominantly in the right pararenal space having three malformed fetuses, one in the right hypochondrium, second in the right lower central pelvis, and third in the left hypochondrium [Figure 1]b. They were displacing the duodenum anteriorly, the right kidney posteriorly with resultant hydronephrosis, and the rest of the bowel loops to the left [Figure 1]c. Lower insertion of the child's cystic duct with common bile duct (CBD) was noted. FIF compressed CBD resulting in moderate dilatation of intrahepatic biliary radicles and cystic duct. The right lower pelvic sac fetus was mostly formed, having spine, iliac bone, ribs, and limbs. Anencephaly was seen with thoracic meningomyelocele and gross anasarca. Fetuses on the right and left hypochondrium were malformed with rudimentary vertebral structures and limbs. Blood supply to all three FIFs was from the superior mesenteric artery.
Figure 1: (a) X-ray abdomen showed three separate areas having multiple radiodensities representing malformed spines and limbs of the fetus, suggestive of 3 fetus-in-fetu (FIF) (arrows); (b) three-dimensional reconstructive images; (c) contrast-enhanced computed tomography showing sac with FIF displacing the duodenum anteriorly, right kidney posteriorly, bowel loops to left; (d) mass stretching duodenum (DU), and ascending colon (AS); (e) Duodenum with dissected common bile duct (arrow); (f) encapsulated fluid-filled sac with visible meningomyelocele (*)

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Total bilirubin (9.7 mg/dL), direct bilirubin (7.2 mg/dL), serum glutamic oxaloacetic transaminase (78U/L), serum glutamate pyruvate transaminase (69 U/L), and alkaline phosphatase (423.6 U/L) were increased. Other routine blood investigations, serum alpha-fetoprotein, and β-human chorionic gonadotropin were normal.

On exploratory laparotomy, a retroperitoneal mass crossing the midline was seen. The duodenum and ascending colon were stretched over the mass, whereas the rest of the bowel was displaced to the left [Figure 1]d. Ascending colon was lifted off the mass. Duodenum was stretched over the mass and densely adhered to it. CBD could not be appreciated as it appeared more like a thin fold of peritoneum. As the duodenum was lifted off the mass, CBD started becoming distinct. CBD was carefully separated from the mass [Figure 1]e. The mass was compressing on the right kidney. After carefully separating the mass from the surrounding structures, it was found densely adhered to the mesenteric root. The blood supply from SMA was ligated and divided. A 600 g intact sac containing 3 FIF was delivered [Figure 1]f and [Figure 2]a. The back of the largest fetus had myelomeningocele [Figure 2]b. Polydactyly was noted in the left lower limb of both the first and second fetuses.
Figure 2: (a) Three fetus-in-fetu connected by cord (arrow), largest fetus was anencephalic with rudimentary facial structures, upper and lower limbs, rudimentary genital structures (penis); (b) posterior surface with meningomyelocele (*), anal dimple (arrow)

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The child had an uneventful postoperative course and was discharged on the postoperative day 6 with normal bilirubin levels. At 1-month follow-up, the child has gained weight. Genetic mapping of the child and three FIFs were similar. Histopathologic examination confirmed the diagnosis of FIF.

   Discussion Top

FIF is a rare anomaly with an incidence of 1 in 5 lakhs.[1] Most patients present in the 1st month of life.[3] They may be asymptomatic or present with the compression of the surrounding organs. The most common site is retroperitoneum (72%) which was also seen in our patient.[3] FIF is generally not kept as a differential diagnosis when a workup for abdominal mass is done because of its rarity. It is usually picked up on radiological investigations.

An X-ray may be suggestive of FIF. However, investigations such as ultrasonography and CECT help to define its relation to the other surrounding structures, which is helpful during surgery. Well-formed vertebral column with other fetal bones is highly suggestive of the diagnosis of FIF, as in our patient. The diagnosis can be confusing if fetal bones are not well formed. Other abdominal masses with calcification such as teratoma, neuroblastoma, and meconium pseudocyst, will have to be ruled out.[3]

There has been a debate regarding the differentiation of FIF from teratoma as it later has malignant potential. FIF is a highly differentiated mass with a discrete vertebral column.[1] FIF is generally suspended in a fluid-containing sac by a pedicle. This pedicle attaches the FIF to the host and contains blood vessels representing umbilical vessels.[4] Teratomas have pluripotent cells with no systemic organization. However, some propose that the pathology is the same in both, but the stages of maturation are different.[3]

Treatment is surgical excision of the mass.[4] FIF is generally covered by a sac which separates it from the surrounding structures and makes surgical excision easy.[2] A single case of CBD injury has been described in FIF, where the CBD could not be differentiated from peritoneal folds.[5] In our case also, there was difficulty in differentiating it from peritoneal folds. However, slow careful dissection in the right upper quadrant was helpful.

Most reported FIFs are anencephalic and acardiac.[3] Evidence of vertebral column (76%), central nervous system (55%), gastrointestinal tissue (61%), genitourinary tissue (36%), pancreatic, adrenal, heart, and primitive lungs have been reported by various authors.[3] Various degree of differentiation has been reported in various reported cases. The largest fetus in our patient had a high degree of differentiation. Phallus and anal dimple being noted earlier, are rare. He even had thoracic meningomyelocele, which has never been reported before in a case of FIF.

To conclude, FIF is a rare cause of neonatal obstructive jaundice. If the duodenum is displaced anteriorly by the mass, it may be difficult to identify the CBD and differentiate it from peritoneal folds because of stretching. Caution is to be practiced while dissecting the duodenum off the mass, as one can damage the CBD. Most commonly, a single fetus is seen. In our patient, three fetuses were seen, and one of the fetuses was highly differentiated and even had meningomyelocele which has never been reported before.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Puranik RU, Joshi P, Jahanvi V, Handu AT, Puli KR. Antenatally detected fetus in fetu case report. BJR Case Rep 2023;9:20230001.  Back to cited text no. 1
Sharma S, Gupta PK, Regmi B, Gupta A, Lamichhane U. Fetus in fetu in an adult female and brief review of literature. Case Rep Radiol 2021;2021:6660277.  Back to cited text no. 2
Prescher LM, Butler WJ, Vachon TA, Henry MC, Latendresse T, Ignacio RC. Fetus in fetu: Review of the literature over the past 15 years. J Pediatr Surg Case Rep 2015;3:554-62.  Back to cited text no. 3
Xiaowen M, Lingxi C, Song L, Shengbao P, Xiaohong Y, Xinghai Y. Rare fetus-in-fetu: Experience from a large tertiary pediatric referral center. Front Pediatr 2021;9:678479.  Back to cited text no. 4
Joshi M, Parelkar S, Shah H, Agrawal A, Mishra P. Foetus in fetu with common bile duct injury: A case report and review of literature. ANZ J Surg 2009;79:651-2.  Back to cited text no. 5


  [Figure 1], [Figure 2]


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