Fetus in Fetu

By George V., Meera Khanna, and Tripta Dutta N e w Delhi, India

�9 This is the report of a case of fetus in fetu. It corresponds to the general ly recognized cr i ter ia for this diagnosis.

INDEX W O R D S : Fetus in fetu.

M ECKEL (CA 1800) coined the term fetus in fetu to describe a condition wherein a

parasitic twin was found included within the abdomen of its partner. A fetus in fetu is a diamniotic, monochorionic, monozygotic twin of its bearer, included with the bearer due to anas- tomosis of the vitelline circulation. 1

Most often the fetus in fetu is intraabdominal and situated retroperitoneally, although other sites have also been reported. It is surrounded by a membrane that is analogous to the amniotic sac and characterized by a single feeding vessel and the absence of a true placenta. The included twin may be grossly deformed due to compression by the host's abdominal organs.

In 1935, Willis, 2 adopted the presence of a vertebral axis (having passed through a primitive streak stage) and an appropriate arrangement of other organs or limbs with respect to the axis as the criterion to distinguish fetus in fetu from teratoma. A teratoma is a true neoplasm arising from embryonic totipotential cells with benign or malignant properties. Teratomas lack a vertebral column (not having passed through a primitive streak stage) and organogenesis but do manifest some degree of progressive uncoordinated growth.

CASE REPORT

Diagnosis A 3-month-old male child was admitted to the pediatric

surgery unit of Safdarjang Hospital, New Delhi, with pro- gressive abdominal distention since birth. The mother had noticed a lump on the left side of the abdomen. A family history of twins was present. The infant was a normal looking baby. Examination of the abdomen revealed a firm, well-

circumscribed, smooth-surfaced mass, 15 x 20 cm in size, in the left side of the abdomen mainly in the lumbar region and extending across the midline in the region of the umbilicus. Plain x-ray of the abdomen showed a soft tissue mass in the left side of the abdomen. Intravenous pyelography revealed a nonfunctioning left kidney. A clinical diagnosis of Wilms' tumor on the left side was made.

Operative Findings In the left lateral position, through a subcostal incision, the

abdomen was opened in layers. A retroperitoneal irregular mass was seen. Part of the mass was cystic and drained 300 to 400 cc of serous fluid. The rest of the mass was solid; part of it was within the cystic cavity. We exteriorized the sac wall completely and removed the mass.

The entire specimen was covered with fine-hair-bearing skin (Fig. 1). A cephalic prominence was present. There was no separation of the abdomen and thorax. A gluteal cleft was present caudally but no external genitalia or anal dimple was seen. Two hands and one foot with well-defined fingers and toes and well-formed nails were present (Fig. 2). Radiologic examination of the specimen revealed small bones in the foot. A longitudinal, midline section of the specimen showed vertebral bodies. Another section, through the lower extrem- ity showed long bones.

Results Postoperative recovery of the patient was uneventful. At

follow-up after 3 months, he was perfectly well. Postoperative intravenous pyelography showed normal function of both kidneys.

DISCUSSION

I n 1961 in h i s c o m p a r a t i v e s t u d y o f t h e f e t u s in

f e t u a n d r e t r o p e r i t o n e a l t e r a t o m a , L e w i s

From the Pediatric Surgical Department, Safdarjang Hospital, New Delhi.

Address reprint requests to Dr. T. Dutta, D-II/30, E A S T KIDWAI NAGAR, New Delhi, 110023, India.

�9 1983 by Grune & Stratton, Inc. 0022-3468/83/1803~)016501.00/0 Fig. 1. Specimen covered with fine-hair-bearing skin.

288 Journal of Pediatric Surgery, Vol. 18, No. 3 (June), 1983

FETUS IN FETU 289

Fig. 2. Two hands and one foot with fingers and toes.

repor ted tha t the fetus in fetu is usual ly sus- pended by a pedicle within a capsule conta ining a l i t t le f lu id) This pedicle is una t t ached to the host and, usually, ends in a th ickened vascular a rea of the sac wall. H e fur ther s ta ted tha t more than one par t of a fetus should be recognizable and the suspending pedicle ident i f iable in order to d iag- nose a fetus in fetu. Also, a ver tebra l column at some s tage of development should be found, together with other bones. Proof of the genuine fetal na ture of a p resumed in t r a -abdomina l fetus in fetu requires the unequivocal x - ray or dissec- t ional demons t ra t ion of par t or the whole of a ver tebra l axial skeleton, 4 a demons t ra t ion tha t will be re inforced if o ther appropr i a t e ly s i tuated bones or organs are shown to be present. ~

The findings in our case, as descr ibed in the case repor t above, suppor t diagnosis of a fetus in fetu as defined by this cr i ter ia .

REFERENCES

1. Lord JM: Foetus in fetu. J Pathol Bacteriol 72:627, 4. Broghammer B J: Foetus in fetu. Radiology 80:844, 1956 1963

2. Willis RA: The structure of a teratoma. J Pathol Bacteriol 40:1, 1935

3. Lewis RH: Foetus in fetu and retroperitoneal teratoma. 5. Numanogolu: Foetus in fetu. J Pediatr Surg 5:472, Arch Dis Child 36:220, 1961 1970