Heteropagus (parasitic) twins: a review

Postnatal imaging of conjoined twins: a customized multimodality approach

Medical imaging plays a crucial role in the management of conjoined twins. The role of imaging is to explore the anatomy, outline the shared organs and determine whether surgery is feasible. It also serves as a roadmap for successful separation. Additionally, imaging helps with counseling parents about prognosis. This review aims to illustrate recent advances in different imaging modalities and their role in the management of the various types of conjoined twins with an emphasis on relevant tips for optimal imaging.

Case report and review of the literature: rare fetus-in-fetu presenting as oropharyngeal epignathus

An epignathus is caused by a continuous spectrum of masses of the oral cavity or oropharynx ranging in its entity from mature teratoma to the exceedingly rare fetus-in-fetu. Due to its location, regardless of the entity, the occurrence of an epignathus is frequently associated with life threatening airway obstruction. Here we demonstrate a case of a fetus-in-fetu presenting as an epignatus. We describe its successful management and review the available literature. Early diagnosis and knowledge of the preoperative workup are essential to enable a multidisciplinary management. Once the airway is secured, surgical excision is the treatment of choice often resulting in a good clinical outcome and prognosis.

Conjoined Twins in Guinea Pigs: A Case Report

Simple Summary

Cases of newborn connected twins, so-called Siamese twins, are well known in humans, laboratory mammals, domestic and wild birds, reptiles, amphibians and fish. This report describes a unique case of newborn conjoined twins in guinea pigs (Cavia aperea f. porcellus). Connected twins in guinea pigs have been very rare, and there are only a few previous reported cases. This report is only the fourth described case of the birth of conjoined guinea pigs. They were born in breeding in the Czech Republic in 2020. The conjoined twins were males connected in the upper body by a cephalopagus-type connection, which has occurred in all three previous reports. The skeletons of both the bodies were connected by a broad shared skull and sternum. Both of the fused bodies had their own hearts and livers, but the lungs were mutual. The issue of this anomaly has not yet been clearly explained.

Abstract

The report describes a unique case of newborn conjoined twins in guinea pigs (Cavia aperea f. porcellus). Connected twins in guinea pigs have been very rare, and there are only a few previous reported cases. The newborns were stillborn in breeding in the Czech Republic in 2020 as two bodies conjoined into one. The external and internal structure of the body and the type of connection of both of the bodies are described. The weights of selected internal organs of the twins are compared with those of normally developed newborn guinea pigs.

Heteropagus twins: six cases with systematic review and embryological insights

PURPOSE

Heteropagus twinning (HT) is a rare anomaly. Six new cases along with a systematic review are described.

METHODS

Six cases of HT managed at two tertiary care teaching hospitals over the last 26 years are described. A PubMed search with words: Heteropagus AND/ OR parasitic twins from 2001 to 2021 hit 183 articles. 36 were added from non-PubMed sources. Finally, 120 cases including 114 from 69 articles and 6 new cases were analysed.

RESULTS

Of the new cases, 2/6 had an antenatal diagnosis. Five were males. 4 autosites had omphaloceles. Split notochord and 2 parasites attached to a single autosite were encountered. 5/6 autosites survived. On systematic review, the most frequent variant seen was rachipagus (n = 50) followed by omphalopagus (n = 46). Limbs were reported in 75 cases. Congenital heart disease was seen in 17/120(14.2%) autosites. Omphalocele and meningomyelocele were the most common extracardiac anomalies in autosites. Weight along with the anatomy and position of heteropagus twins was a better determinant of the mode of delivery than weight alone. Mortality was reported in 12 cases.

CONCLUSION

Autosites in HT generally carry a good prognosis, however, final outcome depends mainly on associated major cardiac anomalies. Meticulous antenatal assessment and preoperative planning are of paramount importance.

LEVEL OF EVIDENCE

IV.

Conjoined twins and conjoined triplets: At the heart of the matter

Conjoined triplets are among the rarest of human malformations, as are asymmetric or parasitic conjoined twins. Based on a very modest corpus of recent literature, we applied the embryonic disk model of conjoined twinning to 10 previously reported cases involving asymmetric anatomical multiplications to determine whether they concerned conjoined twins or conjoined triplets. In spite of their phenotypic similarities, we diagnosed four of these cases as conjoined twins and three of them as conjoined triplets. In the remaining three cases, no definite diagnosis could be made, as essential information was lacking from the reports. We conclude that it is not necessarily the expected duplication or triplication of structures that points to the correct diagnosis in these cases, but the number and mutual position of the hearts they presented with. Considering their rarity we stress to thoroughly investigate and describe internal (dys)morphology in novel cases of (asymmetric) conjoined twins and triplets to further unravel their pathogenicity and come to the correct diagnoses.

A cohort of five cases with asymmetric conjoined twining and literature review

PURPOSE

Asymmetric conjoined twining (ACT) is a form of conjoined twining which is a rare malformation of monochorionic monoamniotic twin pregnancy. Most publications were single case reports. We reported a cohort of five cases with ACT from a single tertiary medical center and reviewed the case reports of ACT over the last decade to enrich the clinical research of this disease and summarized the clinical features of the disease.

METHODS

We reviewed five cases of ACT admitted in Tianjin Children's Hospital from 17 March, 2008, through 7 March 2017. The cohort was analysed from general information, imaging manifestations, separation surgery, histopathological findings, outcome and follow-up. We searched the English literatures on case reports of ACT over the past decade from the PubMed database and presented details about the clinical characteristics, treatment, and prognosis of all cases.

RESULTS

There were four males and one female in our cohort. Among the five cases, two parasites were located in epigastrium, two in rachis, and one in retroperitoneum (fetus in fetu, FIF). All of the parasites were separated successfully by operation in five cases and were confirmed to be ACT by histopathology reports. Four patients made an uneventful recovery except for one case of wound infection. All of them were doing well in follow-up. In the literature review, we found 41 cases of exoparasitic heteropagus twining (EHT) and 63 cases of FIF.

CONCLUSIONS

ACT is very rare and usually diagnosed by prenatal ultrasonography (US). Computed tomography (CT) and magnetic resonance imaging (MRI) examinations are essential imaging examinations before separation surgery to delineate the anatomical relationship between the autosite and the parasite. In general, the separation surgery of ACT is less complicated and the prognosis is better compared with the symmetric conjoined twining (SCT).

Diagnostic Dilemma of an Umbilical Mass in a Newborn Infant - a Twin or a Tumor?

We present the diagnostic dilemma of a neonate with two umbilical soft tissue masses. Case report: The baby had an umbilical mass herniating through the umbilical cord, and another mass hanging from the umbilical mass by a string of tissue. Both masses were amorphous solid soft tissues and the hanging mass had hair on the surface. Clinical diagnosis was umbilical cord teratoma. However, histopathological examination of the masses showed that tissues representing various organs were arranged in cephalocaudal order as in a fetus, revealing that it was a parasitic twin. The hanging mass was probably the cephalic part and the umbilical mass was malformed torso and limbs. Conclusion: This parasitic omphalopagus heteropagus parasitic twin presented as two amorphous masses without externally identifiable anatomic structure, The parasitic twin of omphalopagus heteropagus may have unusual presentations. Histopathological examination was essential to diagnose whether it is a twin or a tumor.

Asymmetric parasitic twins - Heteropagus

BACKGROUND

Asymmetric or heteropagus conjoined twins is a rare occurrence, with an incidence of one case in 1-2 million. Conjoined twins are classified according to their symmetry, place of fusion, and grade of duplication.

METHODS

We report here an extremely rare presentation of parasitic twins not described before. We describe macro and micro anatomic alterations and discuss the aspects of this peculiar presentation and the importance of prenatal diagnosis.

RESULTS

The case of a twenty-three-year-old patient, with monochorionic, monoamniotic asymmetrically-conjoined twin pregnancy, discovered at 29 weeks of gestational age. We believe that this report calls attention to this presentation and the importance of prenatal care and management. The twins were delivered vaginally without life. The twins' combined weight was 1.300 gr. They were bonded in the left cervical region.

CONCLUSION

This report may help to find strategies for clinical decisions in future cases. Antepartum diagnosis is important to the management, preoperative planning, and outcomes. Prenatal imaging exams like echocardiography, CT, MRI, and ultrasonography are feasible and can provide relevant information about malformation severity and prognosis.

Symmetric and ventrally conjoined twins: prenatal evaluation by ultrasound and magnetic resonance imaging and postnatal outcomes

OBJECTIVE

To review the perinatal and long-term outcomes of symmetric and ventrally conjoined twins evaluated prenatally by ultrasound and fetal magnetic resonance imaging (MRI).

METHODS

From March 2010 to January 2019, cases of symmetric and ventrally conjoined twins, who were prenatally diagnosed and referred to the Clínica Diagnóstico por Imagem (CDPI), Rio de Janeiro, Brazil, for prenatal evaluation by ultrasound and MRI were selected. The postnatal information was collected from hospitals where the twins were born and/or treated and from parents' verbal and written information.

RESULTS

Four cases of symmetrical and ventrally conjoined twins were selected. Of these, two were omphalopagi and two thoracopagi. One pair of thoracomphalopagus died early in utero and the other died 6 days after birth. The outcome of the two omphalopagus pairs were separation in emergency surgeries after birth, with neonatal demise of one of the twins due to congenital malformations. In cases of omphalopagi, fetal MRI presented important information of the twins' anatomy before emergency separation of both pairs.

CONCLUSION

Despite the apparently similar conditions of twins with ventral fusion, ventrally attached twins have very different outcomes, most adverse for thoracomphalopagus and related to the singular anatomy of the pair, associated malformations and the extension of the adhesion, requiring individual evaluation of the cases. Fetal MRI is as an important tool for the postnatal surgery management of twin neonates, providing crucial information in cases where urgent separation is required.

Two is a Crowd: Two is a Crowd: On the Enigmatic Etiopathogenesis of Conjoined Twinning

In this article, we provide a comprehensive overview of multiple facets in the puzzling genesis of symmetrical conjoined twins. The etiopathogenesis of conjoined twins remains matter for ongoing debate and is currently cited-in virtually every paper on conjoined twins-as partial fission or secondary fusion. Both theories could potentially be extrapolated from embryological adjustments exclusively seen in conjoined twins. Adoption of these, seemingly factual, theoretical proposals has (unconsciously) resulted in crystallized patterns of verbal and graphic representations concerning the enigmatic genesis of conjoined twins. Critical evaluation on their plausibility and solidity remains however largely absent. As it appears, both the fission and fusion theories cannot be applied to the full range of conjunction possibilities and thus remain matter for persistent inconclusiveness. We propose that initial duplication of axially located morphogenetic potent primordia could be the initiating factor in the genesis of ventrally, laterally, and caudally conjoined twins. The mutual position of two primordia results in neo-axial orientation and/or interaction aplasia. Both these embryological adjustments result in conjunction patterns that may seemingly appear as being caused by fission or fusion. However, as we will substantiate, neither fission nor fusion are the cause of most conjoined twinning types; rather what is interpreted as fission or fusion is actually the result of the twinning process itself. Furthermore, we will discuss the currently held views on the origin of conjoined twins and its commonly assumed etiological correlation with monozygotic twinning. Finally, considerations are presented which indicate that the dorsal conjunction group is etiologically and pathogenetically different from other symmetric conjoined twins. This leads us to propose that dorsally united twins could actually be caused by secondary fusion of two initially separate monozygotic twins. An additional reason for the ongoing etiopathogenetic debate on the genesis of conjoined twins is because different types of conjoined twins are classically placed in one overarching receptacle, which has hindered the quest for answers. Clin. Anat. 32:722-741, 2019. © 2019 Wiley Periodicals, Inc.

Asymmetric Omphalopagus in a Triplet after In Vitro Fertilization: A Rare Case of Conjoined Twinning

Introduction

Asymmetric omphalopagus is a rare situation of conjoined twinning, in which a grossly defective twin is attached to the thorax and upper abdomen of the main twin. We describe a case of an asymmetric omphalopagus accompanied by a normal triplet after assisted reproductive technology (ART) and tried to further characterize the all aspects of the conjoined twins. Case Presentation: Perioperative diagnostic imaging was carried out followed by an autopsy to evaluate all aspects of the parasite accompanied by histological, immunohistochemical, and molecular biological evaluation. The parasite had well-developed lower extremities as well as upper extremities with a cleft hand syndrome. The sex was nondeterminable, but DNA fingerprinting revealed that both parasite and autosite are monozygotic, so are females. There was no sign of any axial skeleton or central nervous system. We found a rudimentary rectum with a nonpervious anus, a kidney, ureter, urinary bladder, and a blind-ending urethra. The blood supply of the parasite was connected to the vessel system of the autosite.

Conclusions

To our knowledge, only two cases of parasitic omphalopagus after ART have been described to date. Altogether, 52 cases have been reported, and in most of them, the parasites were successfully separated.

Parasitic rachipagus conjoined twin: case report

A parasitic twin represents a rare developmental anomaly in which an asymmetrical, nonviable conjoined twin is attached to the host body at the time of birth. Rachipagus is among the rarest of conjoined twin subtypes and typically features a parasitic twin mass attached at the spine. Herein, the authors review the literature and describe the case of a 9-month-old girl presenting with a rachipagus parasitic twin consisting of a fully developed set of lower extremities originating from the midline upper back. After a complete workup to delineate parasite and autosite anatomy, the parasitic twin mass was successfully excised by a multidisciplinary team of surgeons, and the resulting defect was closed in a single stage.

Anesthetic management of parasitic conjoined twins' separation surgery

Parasitic twin is a rare form of conjoined twins with an incidence ranging from 1 in 50,000 to 1,00,000 live births. In thoracopagus type, both hearts are joined together and often are associated with underlying congenital cardiac malformations. The separation surgery is a challenging task for both the surgeon as well as anesthetist due to the complexity of the procedure and long duration of surgery, carrying mortality close to 100% in case of significant cardiac fusion. Here, we are sharing anesthetic management of successful separation of a rare type of parasitic male conjoined twins who had connected hearts and common liver.

A Case of Parasitic Twinning or Caudal Duplication in a Dog

A 6 mo old 13.5 kg (29.7 lb) male intact American Staffordshire terrier was evaluated for a history of supernumerary pelvic limbs, with malodorous discharge from a supernumerary penis. Imaging (radiographs, abdominal ultrasound, and computed tomography with excretory urogram) showed a supernumerary pelvis with associated pelvic limbs, no osseous continuity with the primary spinal column, a colonic diverticulum extending to the supernumerary pelvis, an enlarged left kidney with a ureter connecting to a single bladder, right renal aplasia, a single descended testicle in the primary scrotum, an intra-abdominal cryptorchid testicle, and two unidentifiable soft tissue masses. At surgery, a single ileum was present with a primary and accessory cecum and colon and the accessory colon entering the supernumerary pelvis. The accessory cecum and colon, right kidney, two unknown soft tissue masses, and the single descended testicle were removed. The right kidney had a ureter that anastomosed with the accessory colon at its entry into the supernumerary pelvis. The supernumerary pelvis and hind limbs were not removed. Five months after surgery, the dog was reported to be doing well clinically. Caudal duplication is extremely rare in veterinary medicine. The appearance of supernumerary external structures may indicate internal connections as well.

Successful management of a parasitic ischiopagus conjoined twins in a low-income setting

Ischiopagus parasites are fetal defects attached to a relatively normal twin by pelvis. This is the first reported case of parasitic ischiopagus twins without prenatal diagnosis successfully managed in Mozambique. A multidisciplinary team was involved in the supernumerary limbs excision. After 7 months, the infant has a normal development.

Three-dimensional ultrasound for prenatal assessment of conjoined twins: additional advantages?

Conjoined twins are a rare, but serious, complication of monozygotic twins. Early prenatal diagnosis of conjoined twins is increasingly made with transvaginal ultrasound and color Doppler studies. Most prenatally diagnosed conjoined twins are terminated due to the high perinatal mortality, but advancement in pediatric surgery has allowed for successful postnatal separation in a small number of cases, and some parents may consider this option over termination of pregnancy. It is important to get a detailed prenatal ultrasound for the site and extent of fusion for an accurate categorization. Three-dimensional ultrasound (3DUS) provides images that can facilitate counselling for the parents. Additional information that impacts on diagnosis, prognostication, and perinatal management of conjoined twins could be obtained from selective use of 3DUS, particularly those with atypical fetal union. Most of the proposed additional benefits of 3DUS are based on case reports. Magnetic resonance imaging (MRI) has been increasingly used for the purpose of identifying intricate organ sharing. Because of the rarity of this condition, and the heterogeneity of fetal fusion, added benefits of either 3DUS or MRI for prenatal diagnosis and perinatal management of conjoined twins have not been demonstrated by well-conducted clinical trials. This article aims to review clinical application of various 3DUS display modes in prenatal assessment of conjoined twins, focusing on their potential additional benefits, risks and misuses. 3DUS may help detecting additional findings that are not possible with 2DUS, but, it has not been scientifically shown to improve the survival rate of the twins or reduce maternal morbidity.

High prevalence of same-sex twins in patients with cloacal exstrophy: Support for embryological association with monozygotic twinning

PURPOSE

Previous studies have hypothesized that cloacal exstrophy may be caused by errors early in embryological development related to monozygotic twinning. This study reports the prevalence of twins in a large cohort of patients with cloacal exstrophy.

METHODS

Patients with cloacal exstrophy treated 1974-2015 were reviewed for reports of multiple gestation or conjoined twinning. The genetic sex of the patient and their twin, and any mention of anomaly in the twin were recorded. Neither placental exam nor genetic testing results were available to definitively determine zygosity.

RESULTS

Of 71 patients, 10 had a live born twin (14%), all of whom were of the same genetic sex as the affected patient. One additional patient's twin suffered intrauterine fetal demise, and another patient had a conjoined heteropagus twin. None of the twins were affected by exstrophy-epispadias complex. The rate of twin birth in this cohort was 4.4-7.7 higher than that reported by the Centers for Disease Control in the general population time period (P<0.001), with a striking preponderance of same-sex pairs.

CONCLUSIONS

The highly significant prevalence of same-sex twin pairs within this cohort supports the hypothesis that the embryogenesis of cloacal exstrophy may be related to errors in monozygotic twinning.

LEVEL OF EVIDENCE

2b.

Thoracic heteropagus conjoined twins associated to an omphalocele: Report of a case and complete review of the literature

Heteropagus twins are an extremely rare event with an incidence of 1-2 million live births that represents, sometimes, a real challenge for paediatric surgeons. The majority of cases have complete or partial duplication of the pelvis and/or lower extremities. Thoracic heteropagus conjoined twins is a rare condition in which a grossly defective foetus (the parasite) is attached to the thorax of the main foetus (the autosite). We describe a case of a parasitic heteropagus attached at the chest wall with a rare presentation of giant exomphalos on the autosite. In this situation, the separation procedure was simple after a well-done anatomic study using X-ray, ultrasonography, magnetic resonance and echocardiogram are performed.

Delayed presentation of a heteropagus (parasitic) twin: a case report of a 17-year-old patient

Conjoined twins are rare, but well-described, anomalies. The heteropagus (parasitic) variant, in which there is a fully functioning autosite and a partially formed parasite, is even more rare. Typically, patients with this condition are discovered and treated as neonates or infants. We present an unusual case of an ischiopagus patient presenting at 17 years of age, which appears to be the oldest recorded presentation for surgery of a heteropagus twin in the English literature. The patient had two additional developed lower extremities along with two additional rudimentary upper extremities. The challenges and lessons learned from this rare and complex surgery are discussed.

Going out on a limb for a difficult diagnosis: a case report

Sacral tumors with fetiform features are rare and pose a diagnostic challenge to the ultrasonologist. Sacrococcygeal teratomas (SCT) and parasitic twins can have very similar sonographic features but have different implications to an affected pregnancy. While postnatal histopathology is ultimately necessary to distinguish between a SCT and a heteropagus twin, certain characteristics, such as the presence of a vertebral column and the pattern and rate of tumor growth, may be useful to guide counseling and management decisions.

Prenatal diagnosis of parasitic conjoined twins with three-dimensional ultrasound

Asymmetric and parasitic conjoined twins are extremely rare anomalies of monochorionic monoamniotic twins, consisting of an incomplete twin attached to the fully developed body of the co-twin. Sonographic examination is essential for prenatal diagnosis as early detection of fetal anomalies with poor prognosis provides a chance to deliver the infant vaginally for the mother. We herein describe a case with a prenatal diagnosis of a parasitic twin using three-dimensional (3-D) ultrasound. The clear images obtained with 3-D ultrasound helped in counseling the parents. Making an early prenatal diagnosis of severe fetal anomalies with careful and sophisticated sonographic examinations should be warranted.

Lumbosacral parasitic twin associated with lipomeningomyelocele: a rare occurrence

Lumbosacral parasitic twin is an extremely rare entity. About 200 cases have been reported in the literature. It may be associated with neural tube defects. We encountered a 3-day-old female child with this presentation, who was successfully operated on at the age of about 2 months. Being an uncommon entity, it is presented here.

Conjoined twins: a worldwide collaborative epidemiological study of the International Clearinghouse for Birth Defects Surveillance and Research

Conjoined twins (CT) are a very rare developmental accident of uncertain etiology. Prevalence has been previously estimated to be 1 in 50,000 to 1 in 100,000 births. The process by which monozygotic twins do not fully separate but form CT is not well understood. The purpose of the present study was to analyze diverse epidemiological aspects of CT, including the different variables listed in the Introduction Section of this issue of the Journal. The study was made possible using the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) structure. This multicenter worldwide research includes the largest sample of CT ever studied. A total of 383 carefully reviewed sets of CT obtained from 26,138,837 births reported by 21 Clearinghouse Surveillance Programs (SP) were included in the analysis. Total prevalence was 1.47 per 100,000 births (95% CI: 1.32-1.62). Salient findings including an evident variation in prevalence among SPs: a marked variation in the type of pregnancy outcome, a similarity in the proportion of CT types among programs: a significant female predominance in CT: particularly of the thoracopagus type and a significant male predominance in parapagus and parasitic types: significant differences in prevalence by ethnicity and an apparent increasing prevalence trend in South American countries. No genetic, environmental or demographic significant associated factors were identified. Further work in epidemiology and molecular research is necessary to understand the etiology and pathogenesis involved in the development of this fascinating phenomenon of nature.