Have you ever thought about a situation where you have a twin growing or even found dead inside you from the time you were in your mother’s womb….? Can you just imagine that at least…? Yes, there are cases reported even in our country. An example of this phenomenon was described in 1808 by George William Young.
The term “fetus in fetu” was first used by Johann Friedrich Meckel during the late 18th century. Subsequently, Willis described it as a rare condition where a malformed parasitic twin resides in the body of its host, usually in the host’s abdominal cavity. It was defined as a mass containing a vertebral axis often associated with other organs or limbs around this central axis. Since then, this disease entity has been rarely reported (1:5,00,000).
Foetus in FETU or Parasitic Twin (In detail)
Parasitic twin Or fetus in fetu (FIF) is an extremely rare abnormality (1:5, 00,000) that occurs secondary to abnormal embryogenesis in monochorionic diamniotic (two fetuses with same placenta and genetic material but different amnion) pregnancy where a nonviable fetus become enclosed within a normally developing fetus.
There are two theories of origin concerning FIF. One theory is that the mass begins as a normal fetus, but becomes enveloped inside its twin. The other theory is that the mass is a highly developed teratoma (it is a tumor made of several different types of tissue such as hair, muscle, teeth or bone) Teratoma typically forms in the ovary, testicle or in the region of coccyx.
What is Fetus in fetu???
FIF (Fetus in fetu) has been defined as the existence of a parasitic monozygotic diamniotic fetus in the body of its twin. FIF most frequently inhabits the retroperitoneal region. However, there have been few reports of FIF located in the cranium, sacrum, scrotum, mediastinum and mouth. FIF is considered as a benign condition.
Consequently some researchers have stated that to facilitate the excision that It is possible to leave some section of the capsule in its place. Nevertheless in one case the mass has been reported to recur as a yolk sac tumor after 4 months. This has been attributed to the presence of immature tissues in the small areas and remnants of the capsule of the mass.
Do we have any symptoms for Fetus in fetu??
Normally they have symptoms in such conditions. But rarely cases without any symptoms are also reported. I have seen a woman with no previous symptoms or any discomfort even at the age of 25!! She underwent a medical examination just to rule out the reason for her irregular period. But in her scan, we noticed a large cystic lesion in her abdomen with a heterogeneous mass embedded within it.
Hey, do you know what the strange thing is??? Even though it was so large, it does not disturb her liver spleen kidney or o teen diaphragm. The cyst just pushed her bowel to one side and nothing else. In spite of all these, the surprising thing is that she has not faced any difficulties so far.
RADIOLOGICAL FINDING
There was a large heterogeneous abdominal cyst with a mass with mixed echogenicity and Computed Tomography (CT scans) of the abdomen was performed for further evaluation. CT scan demonstrated a roughly 12 cm diameter density in right upper quadrant with preservation of liver and renal border indicating that this is most likely located Retroperitoneally. The presence of calcification and bone density suggested teratoma or fetus in fetus as the case.
Was that teratoma or Fetus in fetu… ?
This entity is distinguished from teratoma by its embryological origin, it’s unusual location in Retroperitoneal space, it’s invariable benignity and presence of vertebral organization with limb buds and well developed organ system. Diagnosis is made radiologically by the finding of a diminutive vertebral column on a plain abdomen scan.
Conclusion
Fetus in fetu is a congenital abnormality in which we grew with our twin in us. It is considered as a benign tumor within us which is not affecting us but in some conditions it may cause severe infection and can lead to death if it is in cranium. Parasitic twin was found malignant only when a part of the FIF was kept inside. This was found in woman (just for a study purpose) and found that the part showed the characters of a yolk sac tumor.
The treatment of choice is total excision with special attention being given to the fetus’s blood supply which may be directly from the host’s superior mesenteric vessel. Total removal of the malformed fetus has to be performed for FIF is a definite cure.
Read a similar article: “Parasitic Twins – The scientific reasons and case reports“
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