Onfalopagus parasitic fusioned twin: A case report

Abstract

Introduction and importance

The parasitic fetus is a kind of siamese twin, in which one of the twins is reabsorbed and some parts of the body can remain attached to the other twin. It is a very rare event, with a birth incidence that varies from 0.05 to 1.47 cases per 100,000.

Case presentation

This paper reports the case of a parasitic twin diagnosed at 34 weeks of gestational age. Preoperative ultrasonography was performed and the absence of communication between vital organs and the parasite was observed, and surgery was scheduled at 10 days of life. A multidisciplinary team performed the surgical procedure and the child was discharged from the intensive care unit after 3 months.

Clinical discussion

After diagnosis and birth, it is essential to investigate the anomalies found for future surgical programming, and cases of twins who do not share vital organs, for example, heart or brain, have higher survival rates. The treatment is surgical and the objective of the surgery must be resection of the parasite.

Conclusion

The diagnosis still in the gestational period is essential to plan the best mode of delivery and neonatal care, as well as define the surgical schedule. The hospital must be tertiary and the presence of a multidisciplinary team is necessary to perform the surgery in order to present the highest success rates.

Highlights

• •Parasitic twins are joined in the same anatomical location, called conjoined twins.
• •A differential diagnosis must be made with a fetus in a fetus.
• •It is essential to investigate the anomalies found for future surgical programming.
• •A multidisciplinary team is necessary to perform the surgery.

1. Introduction

As defined by Spencer, parasitic twins are twins joined in the same anatomical location, more commonly called conjoined twins. One twin of the pair is severely defective (the “parasite”). Its counterpart (“autositis”) must be mostly intact, although it can exhibit certain congenital anomalies such as heart malformations [1]. The parasite depends on the host's growth, but it rarely contains dysplastic thoracic or abdominal organs. Limbs and trunk are the one possible finding. In almost all cases, prenatal ultrasound can detect the presence of conjoined twins as early as 12 weeks of gestational age [2]. There are still no cases reported of intra-uterine surgery. A differential diagnosis must be made with a fetus in a fetus, in which a non-viable or malformed fetus is engulfed by the fetus of its twin with normal development, generally settling in the abdomen or in the retroperitoneal region. It is believed that one case occurs in every 500,000 births [3], and there are less than 100 cases cited in the literature worldwide [3]. There is no evidence that the parasitic twin can inhibit the autosite growth.

This report describes the case of a male patient, born at term by cesarean section, who was diagnosed with a parasitic twin with an omphalopagus location. He underwent a multidisciplinary surgical procedure in the neonatal period, and evolved well in the postoperative period, being subjected to investigation of other congenital abnormalities and followed up in tertiary reference services. The interesting of this case is that the patient had a shared liver, but other structures were not shared. The majority of parasitic fetus has either the upper limbs or the lower limbs. In this case the parasitic twin has both of them. Ethical Approval was provided by the authors' institution. The work has been reported in line with the SCARE criteria [4].

2. Presentation of case

Male newborn, monozygotic twin pregnancy, cesarean delivery at 37 weeks and 4 days and Apgar score 7/8. The parents were at the second decade of age and there was not a history of comorbidities or use of drugs or other substances during the pregnancy. It was the first pregnancy of the mother. At 34 weeks of gestation, she presented an echographic diagnosis of conjoined parasitic twin with shared liver (omphalopagus), without head pole, showing thoracic structures, limbs, kidney, bladder and umbilical hypertension. Parasitized twin with cardiomegaly, interventricular communication (IVC) and aortic coarctation. The baby can be visualized in Fig. 1 below. Free and informed consent was signed and the study was approved by the ethics committee of the institution.

Fig. 1.

Parasitic fetus soon after birth, evidencing the sharing of structures.

Multidisciplinary surgery was scheduled at 10 days of life. Preoperative ultrasound of the newborn with situs solitus in dextroposition, patent foramen ovale, intraventricular communication, patent ductus arteriosus, showing moderate mitral and tricuspid level. On computed tomography (Fig. 2), the fetus was parasitically connected anteriorly in the thoracoabdominal region, showing: kidney in the transition between the two fetuses, with no identification of the heart, in addition to partial herniation of the liver to the neck of connection between the twins. Regarding vascularization between the twins, it was possible to observe that two arteries irrigate the incomplete twin, both with a diameter of 2 mm, one of which is an extension of the right internal thoracic artery and the other possible persistence of the right umbilical artery (Fig. 3).

Fig. 2.

The fetus was parasitically connected anteriorly in the thoracoabdominal region.

Fig. 3.

Vascularization of the parasitic fetus showing that one of the arteries was originated from the internal thoracic artery.

The resection was initiated at the base of the pedicles of the lower and upper limbs of the parasite, in which a urinary bladder, a structure suggestive of a kidney, was observed, in addition to loops of the small intestine and colon that were continuous and blind. The resected structures can be seen in Fig. 4 below. The newborn had viable intestinal loops, without malformations, liver with a bifurcated lobe, but completely belonging to the patient. No organ sharing between twins was identified. Resection of excess skin and synthesis was performed. The patient had renal insufficiency, with favorable evolution in the postoperative period. The surgery finished after 8 h and there was not important blood loss. Discharge occurred after 3 months of pediatric intensive care. There were not important complications in the immediate postoperative period. The follow up time is 24 months and the child is healthy.

Fig. 4.

Resected structures of the parasitic fetus shortly after surgery, at 10 days of life, representing the lower libs and pelvis, upper limbs and intestine.

3. Discussion

The presence of conjoined twins is a very rare developmental event, with an approximate incidence varies from 0.05 to 1.47 cases per 100,000 births worldwide [3]. The largest published series assessing the incidence of heteropagus twins derives from a US database of 7.9 million births collected over an 8-year period in the 1970s [1]. This study estimated that the true incidence of heteropagus twin births was 0.05 to 0.1 per 100,000. The earliest description of this condition seems to be in the 16th century, when a French surgeon, Ambroise Pare, reported a headless twin with the body attached to the abdomen of one of his patients. [1].

There is still no defined etiology for this condition, but there are two theories for this joint twinning: fusion and fission. Fission is based on the etiology of monoamniotic twins, suggesting that a stimulus applied to the dorsal embryo slightly later may result in incomplete division and formation of conjoined twins. On the other hand, the fusion hypothesis argues that the fusion of two distinct monoamniotic embryonic discs occurs at the site of an ectodermal defect. In each case, subsequent intrauterine events lead to the death of one of the twins, and undeveloped parasitic tissue remains attached to and dependent on the surviving twin. [3]. They can be classified by the most prominent fusion site [5]. Recognized nomenclature includes 8 of these sites: the thorax (thoracophagus), navel (omphaphagus), hip (ischiophagus), buttocks (pygophagus), spine (rachipagus), side (parapagus), skull (craniophagus), and head (cephalophagus).

The most frequent variant, involving union between the thorax and the umbilicus, accounts for 23 (59 %) of these 39 cases and is described by the authors as “epigastric”, “xiphoonphalopagus”, or “omphalopagus” [6], which is the location in this case.

Regarding the possible risk factors for this condition, consanguinity of the mother and biological father was not reported. In addition, no history of maternal tobacco, alcohol, or illicit drug use associated with asymmetrical twinning was reported, with the exception of one mother who smoked half a pack of cigarettes per day during pregnancy. [6]. In the reported case, the mother had no previous comorbidities or history of alcohol or other drug use.

Although there is a marked female preponderance in symmetrical conjoined twins (72 %), the sex difference is less pronounced in heteropagus twins. A study conducted in 2001 reviewed 157 heteropagus twins and found 51 % female [6]. On the other hand, in the reported case both twins were male.

The diagnosis can be made in the prenatal period, around 12 weeks of life, [2] and anatomical details of conjoined organs can be determined by antenatal ultrasound at 20 weeks of pregnancy [7]. After the diagnosis and birth, it is essential to investigate the anomalies found for future surgical planning [6]. In general, computed tomography or regional magnetic resonance imaging, as well as echocardiography, are advisable preoperative imaging modalities. Angiography is not crucial in all cases, as the vascular pedicle has traditionally been determined intraoperatively without resulting difficulty. The parasite blood supply is derived from the autosite and should be studied before surgery. It can also be identified on preoperative CT or MRI angiography [8]. The most common blood supply to the parasite is derived from the falciform ligament, but in this case its origin was the internal mammary. Other vessels that have been identified are left subclavian, epigastric artery and left intrathoracic artery [8].

In the reported case, it was decided to perform computed tomography, which showed a kidney in the transition between the two fetuses, with no identification of the heart, in addition to partial herniation of the liver to the neck of connection between the twins. Accurate and detailed prenatal diagnosis of conjoined twins is possible and essential for optimal obstetric care and parental counseling.

The treatment is surgical and the objective of the surgery must be the resection of the parasite. [3]. The ideal age for separation surgery is controversial. Separation surgery is an elective procedure done two to four months after birth. Sometimes an emergency separation may be necessary if one twin dies, develops a life-threatening condition, or threatens the survival of the other twin. [2]. The outcome of patients with this disorder is variable. Cases of twins who do not share vital organs, for example, heart or brain, such as omphalopagus and pygopagus, have higher survival rates. For ischiopagus and parapagus twins, survival depends on the extent of the union, as pelvic, osseous, and lower genitourinary tract reconstructions are required, with significant long-term morbidity due to the need for additional reconstructive surgery [9].

According to Sharma et al., there may be a single heart, a single liver, small intestine loops crossed from one fetus to another. Other authors describe some cases of urinary tract communication between the parasite and the autositis fetus, and also respiratory [10]. In the case of this article, the twins did not share vital organs or the urinary tract, which technically facilitates the surgery. The majority of parasitic fetus has either the upper limbs or the lower limbs. In this case the parasitic twin has both of them. The separation of both was performed by a multidisciplinary surgical team involving Pediatric Surgery and Plastic Surgery, with a surgical time of 8 h. Afterwards, the baby went to the neonatal ICU and was discharged after 3 months. The child has already been followed up for 24 months postoperatively and had no intercurrences.

4. Conclusion

Although there is a low incidence of heteropagous twin parasites, it is important to carry out the diagnosis even during the gestational period, in order to plan the best mode of delivery, the neonatal care that should be guided and an idea about the possibility and medical schedule. This case presents a parasitic twin with both upper and lower limbs and the preoperative planning was fundamental to ensure success in the child's prognosis.

Consent

Written informed consent was obtained from the patient's parents/legal guardian for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval

This article was approved by the Ethics Committee of the Institution (number 19463419.6.0000.0096).

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author contribution

Oona Tomiê Daronch (corresponding author): writing the paper.

Luiz Paulo Junqueira Rigolon: study concept and writing the paper.

Isabela Picolotto Moraes: study concept and writing the paper.

André Ivan dos Santos Bredley: correcting the paper, chief of surgery of the case.

Camila Giraldi Fachin: correcting the paper, follow-up of the patient.

Renato da Silva Freitas: correcting the paper, follow-up of the patient.

Guarantor

Oona Tomiê Daronch (corresponding author).

Research registration number

Not applicable.

Declaration of competing interest

None of the authors have conflict of interests.