Indian Journal of Pathology and Microbiology

: 2019  |  Volume : 62  |  Issue : 3  |  Page : 430--432

Thoracopagus: Autoptic and radiologic study of 2 cases

Bappa Mandal1, Nelofar Islam2, Suchandra Mukherjee1, Uttara Chatterjee2,  
1 Department of Neonatology, IPGME and R, Kolkata, West Bengal, India
2 Department of Pathology, IPGME and R, Kolkata, West Bengal, India

Correspondence Address:
Nelofar Islam
Department of Pathology, IPGME and R, Kolkata, West Bengal


Conjoined twins are a very rare complication of monozygotic twinning, most common being thoracopagus. Here we report about two cases of thoracopagus male twins illustrating the autopsy details of one case and the prenatal magnetic resonance imaging (MRI) details of another case. While the first case was misdiagnosed as separate twins on antenatal USG, only to be later confirmed as thoracopagus twins after birth, the antenatal MRI done in the second case helped in accurate detection of thoracopagus twins. Bilateral peripheral cortical cysts with dysplasia was noted in one of the twins of the first case, which has not been reported earlier in conjoint thoracopagii. Early prenatal diagnosis of conjoined twins is essential for better counselling of parents regarding post natal surgical management or termination of pregnancy. Importance of prenatal MRI for accurate detection of these cases is thereby highlighted.

How to cite this article:
Mandal B, Islam N, Mukherjee S, Chatterjee U. Thoracopagus: Autoptic and radiologic study of 2 cases.Indian J Pathol Microbiol 2019;62:430-432

How to cite this URL:
Mandal B, Islam N, Mukherjee S, Chatterjee U. Thoracopagus: Autoptic and radiologic study of 2 cases. Indian J Pathol Microbiol [serial online] 2019 [cited 2021 Jan 23 ];62:430-432
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Conjoined twins are monozygotic, monoamniotic, and monochorionic with varying degree and sites of fusion between the twins. The incidence is approximately 1 in 250,000 live births and are more often seen in girls than boys, at a ratio of 3:1. Conjoined twinning arises only when the twinning event occurs at the primitive streak stage of development, about 13-14 days after fertilisation. Of these, about 40% are stillborn and 60% are liveborn and only 25% of them survive long enough to be candidates for surgery. The most frequent type is thoraco-omphalopagus which account for 70% of conjoined twins while the rarest is diprosopus[1],[2] The study of conjoined twins is important because they can be diagnosed prenatally and may be surgically separable. Since this condition, even with surgical separation is associated with high mortality, early diagnosis and management is extremely important.

We present two cases of thoracopagus twins both the cases being boys, diagnosed, as twin pregnancies on routine prenatal ultrasonography. In the first case the twins delivered by Lower Uterine Caeserian Section (LUCS) at 33 weeks survived for 4 hours. An autopsy was thus performed which revealed that besides a common heart and liver, one twin had bilateral renal peripheral cortical cysts associated with lower urinary tract obstruction, which has not been reported earlier in conjoint thoracopagii. In the second case the mother underwent an MRI 3 days before delivery where thoracopagus was diagnosed. The MRI findings of this case are described.

Our cases highlight the need for prenatal MRI at an early stage following diagnosis of twin pregnancy on ultrasound in order to exclude conjoined twins. This would aid in taking timely decision for medical termination of pregnancy at the earliest.

 Case - 1

A 20-year-old primi mother presented to our Department of Obstetrics and Gynaecology at 33 weeks of gestation with signs of premature labour. Her antenatal history was uneventful. A previous ultrasound evaluation done at 29 weeks of gestation revealed two intrauterine live fetuses within two separate gestational sacs. An emergency LUCS was done at 33 weeks gestation at our institution and she delivered live conjoined boy twins that survived for 4 hours.

Before performing the autopsy, consent was obtained and the conjoined twins were studied utilizing whole body radiograph that revealed abdomino thoracic fusion with a single cardiac opacity in the midline. The twins altogether weighed 2303 g. united symmetrically from the upper chest to the umbilicus with omphalocele. There was a single placenta and a single umbilical cord. The autopsy was performed by en block removal of the viscera. The upper extremities were proportional and showed no other associated anomalies. Eight limbs and all digits were present [Figure 1]a.{Figure 1}

The internal examination revealed a single pericardial cavity with sharing of a single large heart weighing 16 g [Figure 1]b and [Figure 1]c. The single common heart had all the four chambers with a single superior vena cava and a single inferior vena cava. There was a single aorta which arose from the left ventricle [Figure 1]d. There was ventricular septal defect involving the muscular part. One of the twins had bilateral hydroureteronephrosis, and a thin walled dilated bladder. The kidneys contained grossly visible cysts varying in size from 0.1 to 0.3 cm. The microscopic examination of the kidney revealed subcapsular cysts of varying sizes and peripheral cortical cysts. There was medullary disorganisation indicating cystic renal dysplasia [Figure 1]e. Thus, a diagnosis of renal dysplasia associated with lower urinary tract obstruction was made [Figure 1]f.

 Case - 2

A 22-year-old primi mother presented to the Obstetrics and Gynaecological outpatient department of our institute at 31 weeks of gestation. The antenatal history was uneventful. The prenatal ultrasound examination done as a routine investigation revealed suspected conjoined twins. An antenatal MRI was done 3 days prior to the delivery for confirmation of the same. The MRI was done using Signa HDX 3T machine in three orthogonal planes (axial, coronal, and sagittal) for better depiction of detailed fetal anatomy. The coronal T2 MRI revealed fusion of the lower part of thorax and abdominal wall with sharing of single pericardial cavity and a common fused liver [Figure 2]a and [Figure 2]b. An emergency LUCS was done at 32 weeks due to premature labour and live thoraco omphalopagus twins, again boys, were delivered, and weighing 2550 g. The twins were alive for five days [Figure 2]c. A plain radiograph of the whole body revealed abdomino thoracic fusion with a single cardiac opacity in the midline which was consistent with the prenatal MRI imaging [Figure 2]d. As the parents refused to give consent for post-mortem imaging and autopsy, these were not performed.{Figure 2}


Conjoined twinning has an estimated frequency of 1 in 50,000 gestations.[1],[3] The classification of conjoined twins is according to the orientation of the two body axes and is based on the most prominent site of fusion. The most frequent type is thoraco-omphalopagus twin, accounting for 70% of conjoined twins.[1],[2] Many types of conjoined twins have been described, the other types being thoracopagus, omphalopagus, pygopagus, ischiopagus, craniopagus, cephalopagus or rachipagus.[4] In all, 40-60% of conjoined twins are still born and among the live births, almost 35% of do not survive beyond 24 hours.[5]

The division of the zygote during the first three days post conception results in the formation of dichorionic diamniotic twins. The division of the embryonic disc after day eight post conception results in monochorionic, monoamniotic twins. Incomplete division of embryonic disc results in conjoined twins. The division of the embryonic disc after day 13 post conception is usually incomplete, resulting in varying degrees of fusion of embryos.[6] The placenta of conjoined twins is always monochorionic and there may be a single cord from the placental surface. Currently, the role of HOX and PAX genes in early embryogenesis are being studied.[7] In both of our cases, the placenta was monochorionic and the umbilical cord was single.

Thoracopagus twins typically, have one large complex heart.[5] The liver is fused into one large mass and 25% of them may share a biliary tree. The large intestines and urinary tracts are usually separate. The lower abdomen, vertebral column, or the lower extremities are not involved in the union. Survival depends upon the type of conjunction and the presence of associated anomalies.[2] In thoraco-omphalopagus, the degree of fusion of the heart determines the prognosis.[5] The presence of a common heart makes the chances for a successful surgical separation negligible.[8],[9] Prenatal diagnosis and exact characterization of extent of sharing are essential for optimum management. The ultrasound is the primary imaging modality for the diagnosis. Prenatal sonographic diagnosis can be difficult, and missed as in both of our cases.[10],[11]

Bilateral hydroureteronephrosis with multicystic dysplastic kidney as seen at autopsy in one of the twins in our first case could not be easily picked up by primary imaging. Lower urinary tract obstruction due to posterior urethral valves is a common cause cystic renal dysplasia. A thoracopagus twin with peripheral cortical cysts associated with lower urinary tract obstruction has not been reported so far. The diagnosis in live born neonates is made by voiding cystourethrogram which demonstrates vesicoureteric reflux and requires timely medical attention. The treatment is usually an immediate vesicostomy followed by definitive treatment.


Each set of conjoined twins being unique, prenatal evaluation of shared organs is of utmost importance for prognostic information. MRI plays a vital role in addition to USG in evaluation of this unusual anomaly. Termination of pregnancy can be offered to the family when the accurate diagnosis is made in the first trimester. Also careful MRI assessment may help to identify associated treatable congenital anomalies like peripheral cortical cysts as seen in our first case. The role of antenatal surgery in conjoined twins is being explored.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.


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