Introduction
Conjoined twins represent rare and most challenging congenital
malformations, the etiology of which remains obscure. The
birth of conjoined twins has always fascinated mankind with
the public’s view of malformed children greatly influenced
by the prevailing culture and religious beliefs. Surgeons over
the years have attempted to separate these twins with variable
success. Systematic preoperative surgical planning is essential.
Knowledge of the anatomy and its variations including
understanding of physiology of the conjoined twins, the use of
newer imaging techniques along with a multidisciplinary team
approach to the complex surgical problem has also improved
outcome. The management of thoracopagus conjoined twins
is not only surgically challenging, and poses moral and ethical
dilemmas, but also has obstetric implications, anesthetic considerations,
and demands significant and complex postoperative
care (
Conjoined twins are always joined at homologous sites,
and the clinical classification is based on the most prominent
site of union, combined with the suffix “pagus” meaning “that
which is fixed.”
but symmetrical and proportional, truly a “harmony in form.”
There are also asymmetrical forms. Eight symmetrical configurations
are recognized, i.e., thoracopagus (chest), omphalopagus
(umbilicus), ischiopagus (hip), pygopagus (rump),
rachipagus (spine), craniopagus (cranium), cephalopagus
(head), and parapagus (side). Asymmetrical or incomplete
conjoined twins (heteropagus) result from the demise of one
twin with remnant structures attached to the complete twin
but the junction remains at or near one of the common sites
of union.(
di-amniotic intra-parasitic twins.
exceptionally rare and their pathogenesis remains even more
obscure
anomalies occurring in one twin, especially reversal of cardiac
situs (71%), congential diaphragmatic hernia, and anomalous
pulmonary and hepatic venous drainage.
Fig. 45.1).1 Conjoined twins are individual and deformedFig. 45.2) Fetus-in-feto are asymmetrical monozygotic2 Conjoined triplets are3 (Fig. 45.3). Conjoined twins often have discordant “E pluribus unum – out of many, one
Ex uno plures – out of one, many”
Incidence
Although the worldwide incidence of monozygotic twinning
is the same in all ethnic groups, the incidence of conjoined
twins appears to be higher in Sub-Saharan Africa, ranging
from 1:50,000 to 1:100,000 live births, or 1 in 400 monozygotic
twin births.
diagnosis of conjoined twins confirms that a large number of
infants die either in utero (28%) or immediately after birth
(54%); in fact, only around 20% survive.
4–6 The natural history that follows a prenatal7 Conjoined twins are monozygotic, mono-amniotic, and
mono-chorionic and are always of the same gender with a 3:1
female preponderance. In human gestations, no factors have
been consistently linked to the incidence of conjoined twins.
Conjoined twins can also occur in association with triplet and
quadruplet pregnancies. Two theories are proposed: The first
is the fission theory in which the fertilized egg splits partially.
Their formation occurs after the primitive streak begins to
form and is the consequence of incomplete separation of the
embryonic plate between 15 and 17 days gestation with two
centers of embryonic growth arising. The second is the fusion
theory, in which a fertilized egg completely separates, but stem
cells (which search for similar cells) find like-stem cells on
the other twin and fuse the twins together. This results in early
reattachment of two separate embryonic discs at the dorsal
neural tube or ventral yolk sac areas at 3–4 weeks gestation.
Spencer’s extensive embryological studies appear to favor the
latter theory (as did Aristotle), but this remains controversial – a
theory that was also held by Aristotle. Although genetically
identical, one infant is almost always weaker or smaller than
45
Thoracopagus Conjoined Twins
Alastair J.W. Millar, Heinz Rode, Jenny Thomas, and John Hewitson
D.H. Parikh et al. (eds.),
DOI: 10.1007/b136543_45, © Springer-Verlag London Limited 2009
558 A.J.W. Millar et al.
Pediatric Thoracic Surgery, 557 the other and may have additional congenital defects. Despite
their anatomical conjunction and same genetic and environmental
factors, different personality traits can be distinguished
from an early age.
8–10 Historical Perspective
In prehistoric times, conjoined twins were depicted in cave
drawings, on pottery or as figurines and often assumed the
female form. In folklore, they were generally regarded as an
omen of impending disaster; eliciting strong emotions ranging
from wonder and admiration to rejection and hostility. Although
malformed children were treated compassionately at times, historical
records show that infanticide was frequently practiced,
and the mother often held responsible for causing the malformation.
11,12
A 17-cm marble statue of a parapagus twin excavated F
twins operated on with a view to
attempting to save one with a more
normal heart. The thoracotomy was
made to incorporate much of the thoracic
wall of the chest of the twin on
the right. (
with a mild chest deformity indicating
successful thoracic wall and skin
closure. (
internal organs including fused liver
F
of the parasite of pelvis, buttocks and legs to the chest of the
autosite
ig. 45.1. (a) Thoraco-omphalopagusb) Note the surviving twinc) MRI showing the sharedig. 45.2. A parasitic thoracopagus twin with heterotopic attachment a b
c
45. Thoracopagus Conjoined Twins 559
from a Neolithic shrine in Anatolia is the earliest example of a
pair of conjoined twins. Three thousand years later Australian
Aborigines inscribed a memorial to a dicephalus conjoined twin
on a rock, and 2,000 years later (700 BC) conjoined Molionides
brothers appeared in Greek geometric art. Double-headed
human figures have also been described in ancient South Pacific
chalk drawings, pre-Columbian clay figures from Mexico, and
in woodcuts from Middle Aged Europe.
Mary and Eliza Chalkhurst, the Biddenden pygopagus
twins, were born in 1100 AD in Kent, England and lived
together for 34 years. The statement filled with pathos “As
we came together, we will also go together” is ascribed to the
surviving twin on the death of her sister. She died 6 h later.
During the sixteenth century, conjoined twins were commonly
described and radically different opinions developed
between the concepts of deformity as divine design and deformity
as an accident – this became known as the “quarrel of the
monsters.” Ambroise Pare, a distinguished surgeon from sixteenth
century described in his book “Of Monsters and Prodigies”
possible causes of conjoined twins (Pare A. Complete
works (Translation) by Johnson T. 1678.). The most celebrated
twins were Eng and Chang Bunker who were “discovered” in
1811 in Siam; and were responsible for the inappropriate term
“Siamese” twins over the years. They were joined by a short
anterior abdominal band containing fibrous tissue and liver.
They were taken to America where they were first portrayed
as human anomalies but later performed as acrobats in a circus.
Later on they became wealthy cotton plantation owners in
North Carolina. They married sisters and between them had
22 children. They died within hours of each other at the ripe
age of 63 years.
The first recorded unsuccessful attempt at separation was
made in 907 AD in Armenia on male ischiopagus twins at
the age of 30 years, and the first successful separation was
performed by Johannes Fatio in 1689 in Basel, Switzerland
on xypho-omphalopagus twins. Both children survived.
13,14 Since then more than 1,200 cases had been reported in the
literature by 2000.
Clinical Features
Thoracopagus twins are joined predominantly at the sternum
but this conjunction may extend to the umbilical region, thoraco-
omphalopagus, which are the most frequently seen variety.
Reportedly, 75% of these cases have various degrees of
cardiac fusion. Prenatal ultrasonography can accurately diagnose
significant cardiac fusion as well as cardiac anomalies,
allowing a choice regarding termination of the pregnancy. Fetal
MRI may be especially useful in defining detail of conjunction
and associated anomalies. Clinical outcome of thoracopagus
twins are related to their cardiac anomalies. The typical
conjunction is along the whole length of the sternum from the
suprasternal notch to the xiphisternum. The join frequently
extends to the upper abdomen and may also be associated
with an exomphalos. The twins face each other and of necessity
the necks are extended in an almost opisthotonic posture.
Each twin has a nipple in the appropriate position in relation
to the fused but separated sternums. The ribs on each side join
a sternum with a wide central oval shaped area of conjunction
in which lie the two hearts most often in a single pericardial
cavity. Lung hypoplasia, usually in one twin more than the
other, along with rib abnormalities may occur. Although the
sternal conjunction is variable, if there is any upper abdominal
conjunction, this usually extends to the umbilicus and is
always associated with extensive liver fusion. In this case, the
foregut of each twin is separate with again a varying degree of
join from the duodenum distally.
Thoracopagus conjoined twins may be classified according to
the degree of cardiac conjunction (Leachman’s Classification):
1. Type A completely separate hearts
2. Type B atrial connection only
3. Type C both atrial and ventricular connections
Diagnosis
Prenatal Diagnosis
The main objective of prenatal diagnosis is to define the extent
of the abnormalities and to counsel the parents accordingly.
Prenatal assessment of the extent of organ involvement is often
F
parapagus twin attached to the one thoracopagus twin
560 A.J.W. Millar et al.
ig. 45.3. Conjoined triplets – one set of thoracopagus twin with a difficult for technical reasons i.e., the position of the fetuses
in utero, and the presence of oligo or polyhydramnios. A team
approach for prenatal counseling and management is highly
recommended combining the experience of the ultrasonographer,
obstetricians, neonatologists, geneticists, pathologists
and pediatric surgeons of all subspecialty disciplines. Recent
advances in ultrasound technology, the usage of color Doppler
flow studies, prenatal MRI and multi-slice CT scans have
improved prenatal diagnosis
15 (Figs. 45.1c, 45.4a, b). F
twins with extensive abdominal conjunction and less
marked cervical spine extension. In this case the hearts were separate,
the liver was fused, and the gastrointestinal tracts were separate.
Successful separation was achieved. (
twins. Note the central pericardium. Although the hearts look
fused in fact they were separate and lay one on top of the other. The
rib cage is slightly asymmetrical with each sternum receiving ribs
from a mirror image of the other twin
ig. 45.4. (a) Scout coronal view prior to CT scan of a set of thoracoomphalopagusb) Axial CT of a set of thoracopagus a
b
In 1950, Gray proposed radiological criteria for diagnosing
ventrally fused twins. Roentological findings are: both
fetal heads are at the same level and in the same plane; an
unusual opisthotonic position of the cervical spines, which
becomes more pronounced with time; an extremely narrow
space between the lower cervical and upper thoracic spines
not allowing the development of a normal thoracic cage; no
change in the relative positions after maternal movement or
manual manipulation. Other features include persistent alignment
of the two fetuses facing each with continuity of the skin
and mirror image body parts with limbs close together.
16 The wide prevalence of the use of prenatal ultrasound
investigations has undoubtedly resulted in an increased
detection of conjoined twins with the diagnosis having been
made as early as 9 weeks gestation.
of the first trimester fetal pole is an early sonographic
feature. However, due to the complexity of conjunction
prenatal diagnosis is more accurate from 20 weeks gestation.
The presence of a single heart and fused liver would
confirm the diagnosis. Additional findings include same sex
twins, a single placenta, more than three umbilical cord vessels
and shared organs. The diagnosis is seldom missed by
those experienced in obstetrical ultrasound. Ultrasound is
also important in evaluating the fetuses for other anomalies
that may affect outcome. Serial scans in the second and third
trimesters may be necessary to further define anatomy.
Fetal echocardiography is essential in establishing the presence
and severity of cardiac anomalies. The ECG is generally
unreliable as two separate ECGs do not rule out significant
sharing of cardiac structures. Serial fetal echocardiography
can be used as a prognostic indicator determining postnatal
feasibility of successful separation. Termination of pregnancy
is offered when fetal echocardiography shows a shared heart,
if the anticipated deformities following separation are extensive
and in the presence of cerebral conjunction. Fetal MRI
is also useful in complex cases to define anatomy and may
help in the decision making. Management of parents who opt
to continue with the pregnancy is aimed at maximizing the
potential for survival of the twins and minimizing maternal
morbidity.
17,18 The bifid appearance Obstetric Implications
In human gestations, no maternal factors have been consistently
linked to the development of conjoined twins. In the
majority, the prenatal course is uneventful. The birth of conjoined
twins may be unexpected, particularly in rural communities,
resulting in obstructive labor with difficult transvaginal
delivery or emergency caesarean section (CS).
can be avoided by planned CS at 36–38 weeks once
the lungs have reached maturity because of the high rate of
stillbirths and dystocia. Children weighing less than 3 kg,
including thoracopagus and ischiopagus have been born vaginally,
and this is made possible through prematurity and
tissue pliability. Most children born vaginally do not sustain
6,19 These complications 45. Thoracopagus Conjoined Twins 561
any damage to the connecting sites (bridges), except where
there is an omphalocoele associated with thoraco-omphalopagus
conjunction. Rupture of the exomphalos and evisceration
of liver and bowel may occur.
labor has also been reported.
Ideally the immediate perinatal management of the babies is
also planned, and in one case in which a twin with a normal heart
perfused the co-twin with a rudimentary heart, the ex utero
intrapartum treatment procedure (EXIT) was utilized because
of concern that the normal twin would suffer immediate cardiac
decompensation at birth.
allowed prompt control of the airway and circulation before
clamping the umbilical cord and optimized management of a
potentially lethal situation with survival of the normal twin.
20 Maternal mortality during7 This EXIT to separation strategy Postnatal Diagnosis and Management
Immediate postnatal management consists of resuscitation
and stabilization of the twins. This is followed by a thorough
physical examination with special investigations to define the
anatomy of conjunction, feasibility of separation, and additional
abnormalities. In general, it is better to wait until 6–9
months age before attempting separation as outcomes are better
and greater preparation can be made in planning the operation.
If emergency surgery is anticipated, all twins should
undergo echo-cardiography and plain roentgenography, which
provides limited but essential information. The site of conjunction
will determine the type and order of special investigations.
The information obtained will determine the surgical
approach, the timing of separation, the allocation of organs
and structures, and the eventual prognosis regarding survival
and functional outcome.
21,22 These imaging studies must include a thorough evaluation
of the cardiovasular, diaphragmatic, hepatobiliary, pulmonary,
upper gastro-intestinal tract, and vascular systems (
45.1
detail, demonstrating organ position, shared viscera and
vascular anatomy. Contrast imaging evaluates the gastrointestinal
tract. A routine search for other anomalies is made.
Radioisotope scanning can assess regional perfusion fields.
Multiplanar imaging techniques provide the best overall anatomical
detail, but CT scan is more useful if bony detail is
required. The use of diagrams, 3D organ models, and surgical
rehearsal of the planned separation procedure if feasible will
ensure the best possible outcome. Despite all these investigations
and careful analysis of findings, preoperative interpretation
may still be difficult with incorrect conclusions drawn.
Table). These investigations should provide excellent anatomical Ethical and Moral Considerations
Ethical considerations, which need to reconcile the best
options for the twins and their parents, are playing an increasing
role in present day decision-making.
of one twin, because of inability to sustain life alone, is the
controversy that evokes the most anguish. The decision
whether to operate or not is rendered more complex by those
about surviving conjoined twins who consciously elected not
to be separated and report that they have lived socially acceptable
lives.
twins who have survived to adulthood and then decide that
separation should be attempted despite the operative risks and
the potential for significant long-term morbidity as life in conjunction
was considered unbearable.
Being conjoined does not necessarily negate individual
development. Religious views may only support minimal surgical
interference, especially when one twin will be sacrificed
at surgery, “We cannot accept one baby must die so that the
other one may live. It is not God’s will,” which differs from
the legal opinion “Why I must order twin baby to die,” or a
twin’s own opinion, “As we came together, we will also go
together,” Eliza Chulkhurst.
23–25 The sacrifice26 Equally, controversy surrounds those few conjoined12 From a practical point of view, the Great Ormond Street
Ethical Guidelines for Conjoined Twin Separation have been
generally accepted; where separation is feasible with a reasonable
chance of success it should be carried out; when surgery
is not possible, custodial care should be offered and nature
allowed to take its course; where one twin is dead or has a
lethal abnormality and cannot survive independently from its
normal twin and if unoperated both twins could die, separation
to save the healthy twin should be attempted.
24 Anesthetic Considerations
Anesthesia for separation of conjoined twins is a complex,
demanding procedure, which is facilitated by having two
color-coded anesthetic teams representing each child.
27,28 Preoperative planning and rehearsals are essential for elective
separations. The extent of cross-circulation between the
T
able 45.1. Investigation of conjoined twins System Evaluation
Cardio respiratory Electrocardiogram
Echocardiography/Doppler ultrasound
MRI/CT with contrast
Cardiac catheterization and Angiography
Alimentary tract Contrast meal and enema
Ultrasound
Radio-isotope scans (liver); technetium
Tc99m-(Sn) colloid and excretion Tc99m
mebrofenin
Radio-isotope scintigraphy
Genito-urinary Ultrasound
Isotope renography
Micturating cystourethrography
Genitogram
Skeletal system Radiography
MRI (spinal cord)
Ultrasound
Vascular Doppler ultrasound
Angiography
Cross-circulation Radio-isotope scan Tc99m-DMSA
562 A.J.W. Millar et al.
infants is unpredictable despite detailed and thorough preoperative
work-up. The preoperative planning should include
availability of additional team members in case of prolonged
anesthesia and surgery, to provide rest. Thoracopagus conjunctions
are associated with a significant risk of anesthetic
complications; therefore, the anesthetic team should also be
aware preoperatively of ethical issues and decisions made in
favor of one twin to the detriment of the other in case where
unfortunate and unavoidable sacrifice of one twin in favor of
the other has to be made. It may only be possible to make
this decision during the separation procedure when the true
anatomy is exposed and defined.
Anesthetic Challenges
Although the neck and head are not often involved in the conjunction
of twins where separation is considered, access to
these structures for anesthesia and vascular access is a considerable
challenge. The higher the conjunction, the greater is the
degree of hyperextension of the babies’ heads and necks, and
the more difficult is airway access (
Thoracopagus twins have the highest mortality of all the types
of conjoined twins
further complicated by additional complex conjunctions at other
levels – either cephalad (head and neck) or caudad (abdomen,
pelvis, spine). In many series, early morbidity and the inability
to separate the twins occurs in this group. The EXIT (ex utero
intrapartum treatment) procedure has presented an unusual
approach to this problem and may offer a realistic option in
managing these infants prior to delivery.
is aimed at maintaining both oxygenation and cardiopulminary
stability for the conjoined twins.
may be performed at this time using placental “cardiopulmonary
bypass” while separation is achieved.
Fig. 45.1).29,27 as an isolated abnormality and may be7,30 The EXIT procedure31 If one baby is not viable, surgery Preoperative Work-Up
All of the above factors will impact on many aspects of preoperative
workup for separation, as well as those investigations
that are necessary prior to separation. The two major factors
that determine survival are the degree of conjunction of the
hearts and their anatomical structures, and how feasible it is
to provide enough cover for the deficit of skin and chest wall
(i.e., ribs and sternum) to enable functional and stable chest
dynamics for both babies after their separation. Therefore,
a thorough evaluation of cardiac and lung function and their
anatomy help the anesthetist plan and manage the surgery
more effectively.
There has been very little emphasis placed on investigating
the respiratory system of these babies. Lung abnormalities
when assessed by bronchoscopy have been identified as tracheomalacia
and the presence of aberrant bronchi. These findings
raise the consideration that all thoracopagus twins should
undergo bronchoscopy during the work-up to surgery.
32,33 Cardiac and circulatory effects
of the conjunction and the anatomical abnormalities
in either or both twins’ hearts. Pericardium is usually shared
but the variation in the rest of the heart structures is unpredictable,
and each set of twins needs to be assessed in their
own right. Angiography under general anesthetic may still be
needed, but it remains a high risk procedure with an unpredictable
response to anesthesia. In a set of twins with venous-pole
sharing, induction of anesthesia resulted in asystole in the twin
with a myopathic ventricle – resulting in brain death in that
twin, an emergency separation with survival of the other.
will depend on the complexity4 Vascular access:
during a prolonged hospital stay. Ultrasound scanning is
useful in finding vessels as they are not always in the normal
anatomical positions.
Venous access may become reduced Airway management
face to face in proximity to each other. The larynx is very
anterior and endotracheal intubation with the aid of a fibreoptic
bronchoscope has been used successfully but depends on
operator ability and the availability of a small caliber bronchoscope
for the neonatal age-group. The use of lignocaine
local anesthesia to the vocal cords is advised. It is necessary
to employ an anesthetist for each twin to manage the airways,
and muscle relaxation should not be administered until the
airway can be controlled. Awake intubation should not be
attempted except in moribund patients. Emergency intubation
in these babies should be avoided if possible. Their deterioration
should be anticipated, and intubation performed in a
controlled planned way.
is usually difficult. These babies lie Positioning for surgery
different disciplines needs to be discussed with each surgical
team. Where cardiopulmonary bypass is required, space for
the bypass machine needs to be identified and the placement
of the cannulas in the patient(s) needs to be clarified. In general,
the babies’ heads are at the top end of a normal operating
table with the anesthetic machines on either side. In older, bigger
twins, it is important to ensure that the twins will fit onto
the table in the space available, and it may be necessary to use
a wider table or modify the one planned for use.
and the changes required for the Equipment Preparation and/or Adaptation
Providing anesthesia for two babies simultaneously requires
organization and preparation of the environment. Numerous
options have been reported. A Carlens (Y) adaptor to fashion
a connector to both babies’ airways to allow for synchronous
ventilation has been used successfully.
a “splitter” for the gas pins at the main supply plug to enable
the use of two machines from one gas outlet in the cardiac
catheterization laboratory.
33 We have used Anesthesia for Procedures Prior to Separation
Computerized tomography scanning (CT), magnetic resonance
imaging (MRI), radioisotope studies, and cardiac catheterization
may all be necessary for determining the anatomical
structures and deciding whether surgery is possible or not. In
complex conjunctions, transthoracic echocardiography may
45. Thoracopagus Conjoined Twins 563
be limited and transesophageal echo, MRI angiography, and
cardiac catheterization with angiography may be required.
33 Surgical procedures prior to separation include examination
under anesthesia for clarification of anatomical structures, bronchoscopy,
systemic to pulmonary shunts where the anatomy of
the heart is abnormal, laparotomy for necrotizing enterocolitis,
decompression of intestinal obstruction where the conjunction
has involved bowel, and placement of tissue expanders. Also
these infants may require surgery that is common for any child,
for example, adenoidectomy for upper airway obstruction.
27 Surgical Management
Preoperative Preparation
Preoperative assessment should include all parameters prior
to normal pediatric anesthesia. Documentation of all investigations
is essential and any anticipated difficulties discussed
with the surgical team. Features of cardiac failure and respiratory
compromise should be identified and treated. In general,
these babies are fairly similar in size so that the medication
administered can be calculated by taking the combined weight
and dividing this in half. Unless there is significant discrepancy
between the sizes of the infants, each baby should have
its own medication given on a dose/kg per individual, regardless
of the cross-over between circulations. Color labeling
for each twin’s medication allows easier identification. In the
period prior to planned surgery for separation, the upper limbs
should not be used for phlebotomy or vascular access to spare
these vessels for use intra-operatively.
Planning of the operating room environment is vital to successful
peri-operative management.
Intraoperative Management
In thoracopagus infants, there is extensive cross circulation.
With complex cardiopagus, inhalational anesthesia given to
one twin may affect the twin not receiving the agent before the
one receiving the anesthetic (personal experience). One has to
be prepared for any eventuality.
During surgery difficulties with vascular access, hemodynamic
stability, temperature control, and blood loss can be
expected. Because of cross circulation, pharmacokinetics, and
pharmacodynamics are inconsistent and altered drug responses
must be expected. Prior to separation, the surgeon may still
not know the exact nature of venous connections, coronary
arterial anatomy, and the branching anatomy of the head and
neck vessels and the true size of the atria and ventricles.
General Principles of Surgery
The surgical separation of conjoined twins presents a great
challenge. Improved survival rates for conjoined twins are due
to advances in perinatal and postnatal diagnostic techniques,
meticulous interpretation of the special investigations, and
correct anesthetic and surgical management carried out by an
experienced multidisciplinary team.
26,29,34–39 Many descriptions of surgical procedures to separate the
various types of conjoined twins have been published.
26,29,35–38,40 Technical details are determined by the anatomy of conjunction,
the allocation of sharing of organs and structures, and the
planned reconstruction. Standard approaches are normally utilized
but variations may demand a novel surgical approach or
alternative techniques. Major factors that will govern successful
separation include the order of separation, the distribution
of organs between the twins, meticulous aseptic surgical techniques,
the reconstruction of divided organs, and structures
and wound closure. It is also necessary to distinguish between
structures that are shared by both twins and those belonging
only to one individual.
often encountered, including previously unrecognized cardiac,
gastrointestinal, and hepatobiliary anomalies. Operation
time is prolonged with the separation of the more complex
thoracopagus twins in the order of 7–13 h.
Emergency surgery is indicated when there is damage to
the connecting bridge or when correctable anomalies threaten
the survival of one or both twins, and there is the possibility
of saving at least one of the twins. Emergency separation has
resulted in up to a 70% mortality rate compared with 20%
for elective procedures, emphasizing the need to stabilize the
infants initially and to postpone surgery until the basic investigations
have been completed.
surgery was necessary to alleviate intestinal obstruction, to
manage a ruptured exomphalos and for deteriorating cardiacrespiratory
status, threatening survival of one or both twins.
Elective surgery is best scheduled for when the infants are
thriving, and all investigations have been completed, providing
a comprehensive and functional description of normal and
fused anatomy. Delaying separation into early childhood may
result in increased postnatal deformities and psychological
problems. If separation is possible and desirable, it is proposed
that surgery should be performed within the first 6–9 months
before an awareness of their condition develops. Motor skills,
sensory integration, and personality need to develop in a
separate state.
8 Unexpected anatomical variations are7 In our experience, emergency41 Skin Closure
Whenever there is extensive sharing of body surface areas, closure
of the disconnected surfaces may pose major problems,
especially when separation is undertaken as an emergency.
42–44 A wide variety of techniques have been described, including
elevation of wide skin flaps, use of relaxation incisions, insertion
of prosthetic material, delayed split skin grafts, and the
use of prior tissue expanders to develop abundant native skin
to allow for tension free closure without causing increase in
intracompartmental pressure, local wound problems or restriction
of respiratory excursion. Cardiovascular and respiratory
failures are the most frequent causes of death in the immediate
postoperative period. Subcutaneous tissue expansion is used to
564 A.J.W. Millar et al.
provide tissue for reconstruction or closure where insufficient
natural tissue exists
poorly tolerated, and it is preferred that both chest and abdomen
cavities be left open if necessary for later staged closure
with plastic reconstruction using skin and muscle flaps or split
skin grafting onto granulation tissue. Vacuum dressings may
assist a more rapid healing, earlier grafting, and wound closure.
Unfortunately, tissue expansion is not always possible, and has
a nearly 60% incidence of complications such as bleeding,
wound sepsis, and skin necrosis. Skin expanders must be correctly
sited, and placements are best tolerated in older infants.
It takes 6–8 weeks to gain maximum advantage.
44–46 (Fig. 45.5). Closure under tension is37 Hepatobiliary and Gastro-Intestinal Tract
The liver is shared in all thoraco-omphalopagus twins. Ultrasound,
CT, and radio nucleotide scanning provide the best
overall picture of hepatic conjunction, the biliary drainage
system including the gall bladder and configuration of the
pancreas. For successful hepatic division, each liver has to
have an inferior vena cava to its own heart; absence thereof is
incompatible with survival after surgery. Hepatic conjunction
is along an oblique plane, and venous connections may consist
of a labyrinth of small venous channels, which may bleed
excessively during surgery. In our experience, hepatic division
has always been possible. Cardiac disconnection must be
accomplished before hepatic division, as a large volume of
blood can circulate through the liver, creating a false impression
that both hearts are able to sustain independent life.
As 25% of thoracopagus twins share a biliary system, the
anatomy of the extra hepatic biliary system (EHBS) needs to
be evaluated. This is best achieved with dynamic biliary scintigraphy
and two gallbladders with independent excretion into
separate duodenums are indicative of two EHBS. However,
intraoperative cholangiography may also be required.
gallbladders do not always equate with two EHBSs, especially
if there is fusion of the proximal duodenum. This may
be demonstrated by upper contrast radiography. Bile drainage
is imperative and in the presence of a single EHBS, one twin
should be allocated the EHBS, while every attempt should
be made to establish bile drainage through a Roux-Y hepaticojejunostomy
in the other twin.
belongs to the duodenum, and is best left with the EHBS if
there is a single pancreas.
The upper gastrointestinal tract from the duodenum distally
is shared in 50% of thoracopagus conjunction. This junction
can extend to the level of Meckel’s point where it will divide
into two separate distal ilea. High duodenal conjunction is a
pointer appointed toward a single or shared EHBS.
38,47 Two5 Anatomically, the pancreas Musculoskeletal System
Children with hemivertebrag asymmetrical or diminutive chest
cavities, and even those with caudal junction are prone to
develop progressive scoliosis of the spine, sometimes in areas
remote from the area of conjunction. Long-term follow up is
therefore mandatory.
Cardiorespiratory System and Chest Wall
The twins should be anesthetized on their sides. The whole of
the twins below the separate cervical areas should be skin prepared
and draped to be included in the operative field. If two
survivors are possible arrangements for two separate operating
tables and teams of surgeons should be made in preparation
for the chest and abdominal reconstruction after separation.
(It may be that a decision has yet to be made on the necessity
to sacrifice one twin, depending on anatomy found.). The
skin incision is made circumferentially along the sternum on
the upper side. If only one survivor is possible then a curved
incision on Twin A’s side of the thorax is made from the cervical
conjunction and curving across to beyond the nipple
and extending caudally down into the abdomen incorporating
a substantial part of the chest wall of the other twin. This
donated thoracic cage can be used to reconstruct the chest wall
after the separation (
and the two hearts inspected.
The thoracotomy approach to the heart is very limited in
terms of assessing the anatomy. The pericardium and hearts
can only be adequately exposed and examined once the incision
is taken across into twin B’s chest, and the anterior of
both hearts can be seen. We found this in both sets we have
done with fused left ventricles: very little could be assessed
until both chests had been opened quite widely.
The cardiac anatomy will of course have been determined to
some extent before surgery, and there would be at least a working
supposition of the anatomy, and what needs to be confirmed.
Decisions are made according to the anatomy. If the two
hearts are separate and can maintain cardiovascular autonomy,
the general surgeons can then open the abdomen and divide
the single liver mass into two along an oblique median plane.
Fig. 45.1b). The pericardium is opened F
twins illustrating the gain in skin cover that can be
achieved
45. Thoracopagus Conjoined Twins 565
ig. 45.5. Skin expanders inserted over the chest wall of omphaloischiopagus If the hearts are completely separate the issue is uncomplicated.
If there is any bridge of tissue the most important
first determination to be made if they are to be separated is
the nature of the coronary supply to each heart, and the coronary
sinus drainage. If they are in any way codependent for
coronary supply or coronary venous drainage they cannot be
separated. Beyond that, atrial connections can generally be
divided, and ventricular connections cannot (or never have
been with any survivors.) In our two sets with ventricular
connections, we elected to leave the fused heart unseparated
totally in twin B’s chest.
The separation of the thorax is then completed from anterior
to posterior. The diaphragms are attached in the normal
manner posteriorly and to a large central tendon and inferior
floor of the pericardium anteriorly. After separation there is
a very large central defect. The pericardium can be replaced
with a Gore-Tex patch but primary skin cover is not possible
unless tissue expanders have been placed prior to separation.
Even with skin expanders and skin cover, the anterior
diaphragmatic attachment needs to be stabilized to facilitate
normal respiratory ventilatory function. Staged closure with
eventual skin graft is another method of achieving wound closure.
What is important is that closure under tension is to be
avoided as cardiac and respiratory compromise will result.
In a case with a single fused heart, one being rudimentary, the
following procedure was carried out. The thoracic cavity was
opened via thoracotomy in Twin A’s side at the level of the fifth
intercostal space. The heart and great vessels were exposed as
far as possible with dissection and carefully examined. The cardiac
abnormalities were as predicted (
Figs. 45.6 and 45.7). Twin A
with a vestigial anterior ventricle and large ventricular
septal defect, with transposition of the great vessels
(Taussig-Bing type), and the major ventricle was fused with
Twin B’s left ventricle. The preoperative decision was that this
twin could not survive with this cardiac anatomy.
had a double-outlet univentricular heart of LV morphology, Twin B
apices towards the right. The left ventricle was fused
to Twin A’s heart with a communication through the common
wall, but there was no VSD or outflow obstruction.
The coronary artery system of twin B was separate from
that of twin A. All the great vessels and left pulmonary veins
(we could not access the right pulmonary veins) and both
venae cavae of twin A were identified. A’s ductus arteriosus
was divided and oversewn, as was the azygos vein and a small
left SVC. Silk ties were placed around the great vessels and
the venae cavae, and around the left pulmonary veins. By
snaring them a trial occlusion of all of the vessels leading to
and from the heart of twin A was attempted. Because there
was a concern for this side of the heart lacking coronary supply
after occluding the vessels, and causing a general arrhythmia
of both hearts, and an attempt was to be made to connect
A’s ascending aorta to B’s with a synthetic shunt. However,
it proved impossible to side-clamp the aortas, so trial occlusion
was done instead. Although it significantly darkened,
and there was some distension especially of the vestigial right
ventricle, A’s heart continued to function well, and after about
10 min looked healthy again. No other adverse events occurred
during the test occlusion and the arterial and venous structures
were individually ligated and divided. Occlusion of the great
vessels resulted in the cessation of circulation in twin A. The
separation was completed with the division of the thoracic
cage well onto Twin A’s side about 2 cm outside the nipple
line. Twin A’s body was removed from the operating table.
The heart now protruded anteriorly from the thoracic cavity
of Twin B. Any attempt at manipulating the heart to put it
within the thoracic cavity resulted in ventricular arrhythmias.
The bony defects in the chest wall were thus closed using a
had dextrocardia, probably situs inversus, with ventricular Fig.
of thoracopagus twins with a fused heart. Note gross chest deformity.
At the time of initial surgery, the chest wall of the other twin was
used to cover the chest wall defect. Any change in position of the
heart resulted in arrhythmia. Late reconstruction of the chest wall
is planned. [A personal comment: Our survivor of almost 10 years
has had a very unhappy course including severe cerebrovascular
accidents from thrombus discharged from the “appendage” heart,
which has also significantly interfered with his own heart’s function.
There is a strong opinion amongst the clinicians caring for him that
we should never have embarked on the procedure in the first place.
I have wondered about it myself, and think I would probably support
doing it again, though we have some experience now on which to
build. (J.H. author)]
566 A.J.W. Millar et al.
45.6. One of a very few survivors (10 years) of a twin from a set section of the ribcage of twin A. Skin closure was achieved
using skin from Twin A.
No twin with ventricular conjunction has ever been successfully
separated with both twins surviving. However there is a
report of thoracopagus twins with two normal hearts joined by
a myocardial bridge who were seperated successfully.
situation where one twin is acardiac or with shared ventricles
successful separation is impossible without sacrificing one
infant. The chest wall and skin of the sacrificed twin can be
used to obtain skin cover and to create a firm structure to protect
the protuberant fused single heart as any dislocation of the
heart from its natural position is likely to cause disturbance of
function. All the main inflow and outflow vessels from one
twin have to be disconnected from the heart and the whole
cardiac complex assigned to the infant selected to survive. We
have had two such infants surviving a sacrifice procedure one
survived 30 days and died from aspiration, and the other is
a long-term survivor of nearly 9 years (
Subsequent reconstruction of the deformed chest is possible
at a later stage.
48,49 In aFigs. 45.6 and 45.7).50 Postoperative Management
Cardiovascular and respiratory failure remain the most frequent
causes of death in the immediate postoperative period. Further
operations may be required for secondary wound closure or
dehiscence and skin grafting. There is also hidden long-term morbidity
and mortality. A number of infants died later from factors
such as unresolved aspiration, bronchopneumonia, poor respiratory
function, gastro oesophageal reflux, and cerebral anoxia.
Postoperative challenges maybe regarded as early or late,
and are determined by all the other predictors of survival after
thoracopagus surgery for separation.
27 Postoperatively, the separated twins should be transported
to the Intensive Care Unit and continually monitored for
bleeding, hypotension, hypothermia, hypoxia, hypercarbia,
acidosis, and electrolyte disturbances. Ongoing volume losses,
respiratory impairment, and cardiogenic instability commonly
occur in separated twins. Cardiovascular, respiratory failure
and sepsis remain the most frequent causes of morbidity and
mortality in the immediate postoperative care. Additional
postoperative complications include chest wall and sternal
insufficiency, diaphragmatic dysfunction, gastro-oesophageal
reflux, and the risk of inadequate skin cover.
Further operations may be required for secondary wound
closure, wound dehiscence, and vascular access.
Results
Over a period of 43 years (1964–2007), the Red Cross
War Memorial Children’s Hospital has managed 47 sets of
symmetrical and asymmetrical conjoined twins. The relevant
Fig.
and atrial arrangement of
a set of twins with a single heart
after separation to save the life
of one
45. Thoracopagus Conjoined Twins 567
45.7. Diagram of the ventricular information is shown in
toward premature labor and CS for obstructive labor. There
were few postnatal maternal complications.
The surgical management of conjoined twins has been
divided into three categories (
1.
which were thoracopagus, 1 ischiopagus, and 1 triplet.
Intrauterine death was either due to elective abortion (13–
32 weeks), obstetric error or complex cardiac anomalies
incompatible with life, confirmed by postmortem examination.
These fetuses were lost during the 26–30th week of
gestation. Six sets of thoracopagus twins were born alive
but subsequently died from complex cardiac anomalies
with cardiac failure at 9 days – 2 months postbirth. One
symmetrical ischiopagus twin died as a result of a perforated
colon and peritonitis.
2.
on three symmetrical sets during the neonatal period.
A thoracopagus twin deteriorated on day 15 necessitating
emergency separation. Great difficulty was encountered
closing the thoraco-abdominal defects primarily, which
resulted in irreversible respiratory failure. An omphalopagus
twin was born with a ruptured exomphalos with evisceration
of liver and loops of bowel and demise of the other. The one
parapagus twin was moribund at birth necessitating surgical
separation within 17 h once preliminary investigations were
performed. Only two of six children survived separation
with one dying at 6 weeks from bronchopneumonia.
3.
on 14 sets at ages ranging from 4 days to 11 months, when
tissues were still pliable and the infants in the optimal
physiological state. Reasons for the wide variation included
allowing time for the infants to grow and to bond with their
families and also completion of the multitude of investigations
required. On occasion it was also necessary to resolve
complex moral and ethical issues when there was a threat
to the survival of one or both infants. Additional delay was
due to the use of tissue expanders in two sets of ischiopagus
twins to facilitate wound closure, repeated operative
rehearsals, and reordering of selected investigations, where
uncertainty existed. Twenty-two of a potential 28 children
survived. In one set of thoracopagus twins with a combined
complex heart, the decision was made to sacrifice the one
child, with the parents’ permission to save the life of his
brother. This child is the only long-term survivor following a
procedure of this kind.
An assessment of the cardiac anomalies encountered in 16
thoracopagus infants during presurgical investigations, during
surgery and at postmortem, revealed the following: a shared
pericardial sac with separate hearts in 5, conjoined hearts in 8
who manifested varying types of atrial or ventricular fusion,
while 3 had a single heart.
Other abnormalities identified included anomalous pulmonary
veins, atrio-ventricular septal defects, hypoplastic
pulmonary vessels, abnormal vena caval drainage and abnormal
origin of major arterial vessels from the aortic arch 9.
Table 45.2. There was a tendencyTables 45.3 and 45.4).Nonoperative management: Ten sets were stillborn, 8 ofEmergency separation: Emergency operations were performedElective separation: Elective separations were performed Surgical Outcome
The surgical outcome of our series is depicted in
Table 45.3 and compared with two international series in
overall survival for symmetrical twins was 33.3% but 64.7%
for those that were operated upon. Emergency surgery had
Table 45.4. The T
(based on data from 54 sets of twins).
able 45.2. Obstetric implications implications of conjoined twinsa Maternal history
Maternal age in years 23 (16–45 range)
Parity – Nulliparous 38% (17 of 45 sets)
Family history of
twinning
14.3% (8 of 54 sets)
Stillbirths 39.6% (21 of 54 sets)
Antenatal diagnosis 41% (32 sets)
Birth
Presentation:
° Breech 52% (13 of 25 sets)
° Vertex 48% (12 of 25 sets)
Vaginal delivery 41% (19 of 46 sets)
Mean gestational age
weeks
35.3 (20 sets)
Combined weight/kg 3.9 (2.7–4.9 in 13 sets)
Elective Cesarean
section
59% (27 of 46 sets)
a
Obstetrical information extrapolated from available data 5 T
able 45.3. Conjoined twins 1964–2006. Sets Operations Survivors
Symmetrical twins
Thoracopagus 23 9 10
Omphalopagus 1 1 1
Ischiopagus 5 3 6
Pygopagus 2 2 4
Parapagus 1 1 1
Craniopagus 1 1 0
Cephalopagus 1 0 0
Total 34 17 22
Incomplete or asymmetrical twins
Ischiopagus 4 3 3
Parasitic 5 5 5
Fetus in fetus 3 3 3
Total 12 11 11
Conjoined triplets
1 0 0
T
able 45.4. Outcome in three major studies on conjoined twins. Symmetrical twins
Operated
Emergency
surgery Elective surgery
Source
No of
sets
Not
operated
sets
No of
sets
No of
Survivors
(%)
No of
sets
No of
survivors
(%)
Spitz and Kiely
O’Neill
Red Cross Hospital
Series
34 17 3 2 (33) 14 20 (72)
34 22 6 7 4 (29) 9 15 (83)37 18 5 5 1 (10) 8 13 (81) 568 A.J.W. Millar et al.
a dismal outcome with only two infants surviving (33%.).
Asymmetrical separation had a 92% survival rate.
Late deaths are reported in those babies who have been separated
but have poor respiratory dynamic function and have
died from aspiration.
to morbidity and mortality of these babies.
27,4 Sepsis is another significant contributor Conclusions
Prenatal diagnosis allows careful planning for delivery and for
preoperative assessment. Emergency surgery may be required,
but it is preferable to delay surgery to allow growth and the
completion of investigations. Inevitably, the ultimate prognosis
will depend on the state of the conjoined organs and the
potential for successful separation. Tragically in some, separation
will not be possible. Detailed preoperative assessment is
essential to determine the best surgical approach, reconstruction
methods, and ultimate outcome. Despite successful separation,
some children are left crippled and disabled, requiring
life-long follow-up and care.
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McCoy sisters
