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Siamese Twins - the 20 Years Experience in United Arab Emirates

Amin El-Gohary

Department of Pediatric Surgery, Burjeel Hospital, Abu Dhabi, United Arab Emirates



Amin El-Gohary

Burjeel Hospital

Abu Dhabi P.O.Box 7400

United Arab Emirates

Phone: +97150 6225532

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.




Conjoint twins are rare anomalies that excites medical and public interest and carries with it moral and surgical challenges.

Material and methods

In the years 1985 to 2004, 9 pairs of conjoined twins were managed at Mafraq Hospital in the United Arab Emirates (UAE): two dicephalus, three teratopagus, one pygopagus and three thoraco-omphalopagus.


Successful separation was achieved in all parasitic twins (teratopagus), as well as the pygoagus twins. The first pair of the thoracopagus twins died at 9 months after successful separation from acute lymphoblastic leukemia; the other pair of twins died 1 month postoperatively. One dicephalus and one thoraco-omphalopagus died shortly after birth before surgical intervention.


Successful separation of conjoined twins requires teamwork, detailed planning, rehearsal and anticipation of problems that may arise during or after separation.

Keywords: conjoined twins, siamese twins, diphagus, thoracopagus, omphalopagus, teratopagus, pygopagus




The birth of conjoined twins presents challenging medical and surgical problems that require teamwork, detailed planning, rehearsal and anticipation of problems that may arise during or after separation. At times, separation of conjoined twins requires moral and ethical decisions, especially if separation would mean that one twin would be severely mutilated or had to be sacrificed [1]. The most common variety of conjoined twins is the thoraco-omphalopagus type, accounting for 30%±40% of most series [2, 3] and 70% in ours.

Case reports

Case 1

Male thoraco-omphalopagus twins were born in October 1985 by caesarean section in the second pregnancy of a 28 year-old mother. Their combined weight was 6.7 kg. Examination revealed that they were joined from the lower 6 costal cartilages to the umbilicus, had a shared centrally situated liver (Fig. 1A) but separate gastro intestinal tracts (Fig. 1B). At fifty two days after careful planning and several rehearsals, they were successfully separated. (Fig. 1C) The use of intravenous fluorescence was helpful in delineating the fusion line and minimizing blood loss during liver separation. The skin defect was bridged with a silastic membrane under which granulation tissue formed and later was removed at 3 months. They remained well until May 1986, when they presented with weakness and abdominal distension. Both were pale and had massive hepatosplenomegaly. Hematological studies including bone marrow aspiration showed that both had acute lymphoblastic leukemia (ALL- L1), from which both died 3 months later while receiving their third course of chemotherapy. As far as we can ascertain, this is the first case of ALL in conjoined twins.

Figure 1: 1A - 1st set male thoraco-omphalopagus twin; 1B - Radiology showing separate GIT with central shared liver; 1C: 6 month after separation


Case 2

Male thoraco-omphalopagus twins were diagnosed antenatally by ultrasound at 34 weeks and transported before delivery to our hospital. The twins were delivered in May 1987 by caesarian section at 35 weeks of gestation, the eighth pregnancy of a 33-year-old mother. Their combined weight was 3.77 kg. They had poor Apgar scores and had to be ventilated shortly after delivery. They died 7 days later before completing the relevant investigations. Post-mortem examination showed joined hearts with complicated anomalies of the great vessels.

Case 3

Female thoraco-omphalopagus twins, also diagnosed antenatally, were referred to Mafraq Hospital at 34 weeks of gestation. They were delivered 1 week later in November 1988 by ceasarian section, the eighth pregnancy of a 35-year-old mother. They had extensive fusion of the chest walls and crowding of the mediastinal structures (Fig. 2A). The heart of twin A was inside the chest of twin B (Fig. 2B). They had to be mechanically ventilated soon after birth, but 1 month later could be maintained on nasopharyngeal oxygen. They shared a common liver, duodenum and part of the upper jejunum. The two atria were in communication, with resultant massive cross-circulation (Fig. 2C).

Figure 2: 2A -  3rd set of female thoraco-omphalopagus twin, 2B - Twin B heart projection into twin A chest cavity, 2C - Illustration of joined GIT

Subcutaneous tissue expansion was started at the age of 50 days, but this process had hardly commenced before twin B aspirated during a feed and sustained permanent brain damage. Unfortunately, twin B’s heart was the one in the normal anatomical position, and she therefore had the better prognosis. It was clear that if the other twin was to be saved, a premature attempt would have to be made to separate them; this was hampered by the parents’ refusal to sacrifice the brain-damaged twin. The operation was carried out at the age of 3 months by three surgical teams: cardiac, plastic, and pediatric. The common jejunum was given to twin A, and a jejuno-jejunostomy established continuity in twin B. The atrial communication was easily closed by the cardiac team. The ectopia cordis of twin A presented a more formidable problem that was addressed by forming an artificial cage of wire attached to the costal cartilages and covered by silastic and dacron membranes. The same materials were used to cover the large abdominal defects of both twins. The combined procedure took 11 hours and 45 minutes. Both twins did reasonably well in the early post-operative period, but twin B did not recover from her brain damage and died 1 month later. Twin A, who needed special positioning to warm the projecting heart, died 2 months later.

Case 4

Female dicephalus twins diagnosed antenatally and delivered in January 1991 by caesarian section were the second pregnancy of a 29-year-old mother. Both required ventilation soon after birth and died 4 hours later. The parents refused a post-mortem examination.

Case 5

Female dicephlus was born preterm at 33 weeks gestation to a 29 years old primigravida mother. They shared one uterus, one vagina and one anus. The twins had sudden unexplained sudden infant death syndrome death before they were fully investigated. Parents refused post mortem examination.

Case 6

A male baby with a parasitic teratopagus twin (Fig. 3A) was born at full term by normal vaginal delivery on February 1988 to a 26-year- old primigravida. The parasite was projecting from the oral cavity of the normal twin. The parasites infiltrated the oro-, nasopharynx and submandibular region. Because of early respiratory distress, emergency surgery to remove the obstructing parasite was carried out 4 hours after birth. The parasite was a cauliflower shaped mass containing a collection of well-developed leg and deformed, incomplete organs including brain tissue, a spinal column, an empty scrotum, and a section of intestine (Fig. 3B and 3C). Histopathology revealed a mixed teratoma with an element of embryonal carcinoma at its base. Six months later, he developed a recurrence in the submandibular area that was successfully removed. During this time it was established that he had a single ventricle, but he has remained reasonably well and is being followed by our cardiac surgeons.

Figure 3 - Sixth set: 3A - Parasitic twin projection from the mouth, 3B - The teratomatous parasitic twin, 3C - Post-operative appearance

Case 7

A female teratopagus born in July 1991 at full term by normal vaginal delivery were the sec- ond pregnancy of a 25-year-old mother. This was described as a “third limb’’ variety arising from the posterior aspect of the iliac crest and coccyx. The limb was successfully excised when the baby was 1 week old. Histopathology did not reveal any teratoma structure.

Case 8

A case of caudal duplication (Fig. 4A), born in Somalia in October 1997 was referred to Mafraq Hospital for surgical management at the age of 13 months. The CT scan and MRI exam revealed well-developed lower limbs with a significant blood supply arising from the internal iliac vessels on both sides. The extra limbs were removed after ligating the feeding vessel (Fig. 4B and 4C).

Figure 4: Eight set - 4A - Parasitic twin, caudal duplication, 4B - The excise caudal duplication, 4C - Post-operative appearance.

Case 9

A set of 2 male pygopagus twins were born at full term by normal vaginal delivery in a poor rural area in Sudan, in April 2003. Their lower spines were fused and they shared a common anus and one penis. They were referred to Mafraq Hospital at the age of 16 months for further management. Initial evaluation showed they were joined at the sacrum and shared a normal appearing phallus. Four normal testes were palpable in 4 separate hemiscrotum. Sensation and motor function of the lower limbs were normal.

Computed tomography and magnetic resonance imaging showed a fused lower sacral region (S1 – S3) with spinal cords sharing one continuous dural tube. They were also found to share a common rectum on barium enema. The muscle complex around the common anus was found to split equally on the lateral side of the shared anus. Evaluation of the genitourinary tract showed 4 normal kidneys and ureters, separate bladders and a fused posterior urethra at the level of the membranous urethra extending to the external urethral meatus. A three-dimensional animation and a pelvic model were utilized during both planning and operative phases of the separation and proved to be of great value in preparing the separation. It clearly showed the anatomical fusion at the bony level and demonstrated the presence of 4 corporal bodies, which raised the hope of potential penile separation. Two tissue expanders were used at the lower sacral area on both sides for 3 months being gradually inflated to obtain adequate tissue cover and to attempt to separate the fused urethra and anus.

Operative procedure: Two anesthesia teams and 4 international surgical teams (plastic, neurosurgical, colorectal and pediatric urology) were involved in the separation. The surgical team worked in succession according to the rehearsed plan. Cystourethroscopy showed a normal anterior urethra that diverged into 2 separated posterior urethrae at the level of the prostate. The bladder was mildly trabeculated in twin A and moderately trabeculated in twin B. The 3 fused lower sacral segments were separated, allowing a clear view of the dural tube which was opened to secure the neural structures, than the common dural sac was divided and repaired. The 5-cm common rectum passing through the levator muscles was split longitudinally into two tubes with preservation of the lateral muscle complex on both sides. This opened the way to the fused urethra and it was then feasible to identify the line of fusion between the corporal bodies. The anterior urethra was not wide enough to allow the creation of two separate urethral tubes, and therefore we opted to create 2 perineal urethrostomies and cover the corporal bodies with redundant penile skin.

The sacral and perineal defects were covered by approximating the perineal muscles towards the midline and covering them with the gluteus maximus muscle. The new anus was placed as near as possible to the supposed anatomical site and the skin was mobilized to cover the defect with minimal tension. Both twins had an uneventful recovery, were independently mobile and were discharged from the hospital after 3 weeks.

Eight months later both twins underwent repair of their perineal hypospadias. The urethral plate in both twins was wide enough to allow for a tabularized incised urethral plate reconstruction of a new urethra (TIPS) over size 10 silastic catheters that were left in the bladder for 8 days. Twin A achieved urinary control with occasional dribbling, while Twin B needed intermittent catheterization with evidence of a neuropathic bladder. As for bowel control, Twin A achieved reasonable control but Twin B had frequent soiling.

As the MRI scan has showen that the muscle complex is only present on one side of both twins, we opted to wrap the laterally displaced sphincter around the rectum of Twin B as he had poor bowel control. The muscles representing the anal sphincter were wrapped circumferentially around the lower rectum and sutured to themselves anteriorly. Soiling was reduced gradually to 2-3 times a day with occasional soiling at night and he was able to have a good bowel movement 3-4 times per day with no perineal excoriation.


Identical twins are the result of complete separation of the inner cell mass of the blastocyst at up to 7 days after fertilization. Conjoined twins are probably the result of monozygotic twins in which the embryonic disk divides later and incompletely [6]. The incidence of conjoined twins varies between 1/80,000 and 1/100,000 [3, 6, 7].

The cause of conjoined twinning is unclear, although such outcomes have been induced in experimental animals by agents such as magnesium deficiency, butyric acid, intercurrent infection, exposure to insecticides, and irradiation [7].

The total population of UAE in 1995 was 2.4 million. The total annual delivery rate between 1985 and 1992 was between 44,000 and 51,000. The number and pattern of deliveries cannot explain the sudden occurrence of this large number of conjoined twins. However, this phenomenon coincided with the Iraq-Iran war, where many chemical weapons were known to have been used. UAE is in close proximity to both countries, and on the basis of the experimental evidence described above it does not seem fanciful to suggest a connection. Most reported series of conjoined twins show a strong female preponderance [2, 7], which was not found in our series.

The birth of the first set of conjoined twins alerted us to the possibility in all twin pregnan- cies. Subsequently, all cases were diagnosed antenatally and transported before birth, which improved the chance of obtaining live born twins. This series highlights some unique pre- sentations and problems. Perhaps the most dis- appointing was the loss of the first set of twins, who developed ALL 6 months after technically successful separation. This was thought to re- sult from an early leukaemogenic event occur- ring some time before the separation affecting the haemopoietic cells with features of an early B-cell lineage [5].

The fifth set was a unique case of teratopagus twins in which the parasite was protruding from the mouth of the normal twin. We could not trace any similar case in the literature, and in all reported series the parasite was attached to the trunk or the chest [8-10].

The third set of twins presented us with a severe ethical dilemma. From the outset, it was clear that the twin who’s heart was within the thoracic cavity would have the better chance of a long-term outcome. Unfortunately, this twin aspirated a feed and during the respiratory crisis sustained severe brain damage. Assessing the severity of the damage was made more difficult because of the massive cross-circulation between the twins. In the absence of clear, undisputed evidence of severe brain damage, the parents were unable to face the sacrifice of the apparently damaged child. We were obliged to give equal opportunity to both twins, which sadly, but perhaps predictably, failed. This case highlights some of the ethical and moral problems encountered in the management of conjoined twins [1, 11].

The last set of pyegopagus twin was a great success, and is a source of pride to the medical community in UAE. As far as we can ascertain, this is the first case of male pygopagus twins who presented with fused corporal bodies who have been successfully separated with fairly good results [12]. Preoperative assessment of the fused organs can be achieved by conventional radiology; however, three-dimensional animation and pelvic modeling [3], which were utilized both during the planning and the operative phases of the separation have proved to be of great value in achieving the best possible result. They were particularly useful in identifying the single dural tube, fused sacral vertebrae and fused corporal bodies of the urethra which culminated in the separation of two functional penile shafts.




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