Prenatal MRI of Heteropagus Twins

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.

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.

Imperfect twinning: a clinical and ethical dilemma

OBJECTIVE To review the history, epidemiology, etiology, gestational aspects, diagnosis and prognosis of imperfect twinning. DATA SOURCES Scientific articles were searched in PubMed, SciELO and Lilacs databases, using the descriptors "conjoined twins", "multiple pregnancy", "ultrasound", "magnetic resonance imaging" and "prognosis". The research was not delimited to a specific period of time and was supplemented with bibliographic data from books.

DATA SYNTHESIS

The description of conjoined twins is legendary. The estimated frequency is 1/45,000-200,000 births. These twins are monozygotic, monochorionic and usually monoamniotic. They can be classified by the most prominent fusion site, by the symmetry between the conjoined twins or by the sharing structure. The diagnosis can be performed in the prenatal period or after birth by different techniques, such as ultrasound, magnetic resonance imaging and echocardiography. These tests are of paramount importance for understanding the anatomy of both fetuses/children, as well as for prognosis and surgical plan determination. CONCLUSIONS Although imperfect twinning is a rare condition, the prenatal diagnosis is very important in order to evaluate the fusion site and its complexity. Hence, the evaluation of these children should be multidisciplinary, involving mainly obstetricians, pediatricians and pediatric surgeons. However, some decisions may constitute real ethical dilemmas, in which different points should be discussed and analyzed with the health team and the family.

Thoracopagus parasites in two sets of twins: evidence for the fusion theory

We report two sets of parasitic twins attached in the thoracic region. Exomphalos major in the autosite was present in both cases. While in case 1, the autosite could be salvaged after easier dissection, in case 2, the autosite could not be salvaged due to the presence of the life-threatening anomalies. The presence of a right-angled communication between the gastrointestinal tracts of the autosite and the independent tactile responses of the parasite from that in the autosite supports the 'fusion theory' to explain the fusion of the embryos that could have led to this defect. The presence of the ano-rectal malformation and common bile duct dilatation exclusively in the parasite appears to be the result of the abnormalities in the endodermal-mesodermal interactions, probably due to the relative positioning of the parasite with respect to the autosite.

Imaging of conjoined twins

The incidence of conjoined twins is estimated to be around 1 in 250,000 live births. There is a distinct female predominance. In this paper the imaging of conjoined twins both antenatally and postnatally is reviewed, in particular taking into consideration recent advances with multidetector CT. Accurate counselling of parents regarding the likely outcome of the pregnancy and the likelihood of successful separation is dependent on good prenatal imaging with ultrasound and MRI. Planning of postnatal surgical separation is aided by accurate preoperative imaging which, depending on the conjoined area, will encompass many imaging modalities, but often relies heavily on CT scanning.