What Is Fetus in Fetu?

Fetus in fetu is an extremely rare congenital anomaly where a growth that superficially resembles a fetus develops inside a patient's body, often in the abdomen. The growth is parasitic and cannot survive independently, as it lacks a number of key organs, including the brain. It can also endanger the patient with its parasitic use of the patient's blood supply for nutrition. Treatment involves surgery to remove the growth and check for any complications inside the patient.

There are two possible mechanisms for this unusual condition to occur. It may be a form of teratoma, a tumor that arises from undifferentiated cells. Teratomas contain a jumble of tissue types including skin, hair, and bone, and sometimes have a very organized appearance. They may have structures like limbs, for example. These growths can become malignant in some patients. Other cases of fetus in fetu may be the result of errors in the growth of a set of twins, where one twin engulfs the other during fetal development.

Often, fetus in fetu is diagnosed in the first months of life. The patient may have a noticeable abdominal growth and could show signs of fatigue and restlessness. Some fail to thrive because the fetus in fetu absorbs their nutrients. Medical imaging and a physical examination can reveal a growth, and surgery will resolve the issue. In a few rare cases, patients have survived into adulthood with the growth intact, seeking treatment when it becomes a problem.

Cases often attract media attention because the condition is rare and may be a topic of interest. As with conjoined twins, fetus in fetu can present an interesting medical challenge to doctors, who must figure out how to safely remove the growth. They may need to consider the extent of attachment to the blood supply and a number of other issues when planning the surgery, with the goal of getting the tumor out and preserving the patient's bodily functions.

It is estimated that fetus in fetu occurs in about one in every 500,000 births, and very few cases have been documented in medical literature. The condition is a source of fascination for some artists, who have depicted it in film, television, and novels. It is important to be aware that despite the name, fetus in fetu does not refer to a true fetus; it cannot survive independently, lacks a brain, and is a parasitic growth, not another human being.