Minimally Jointed Symmetrical Pygopagus Twins - Successful Surgical Separation.

Conjoined pygopagus accounts for about 17% of all conjoined twins and commonly share the gluteal region, terminal spine, lower gastrointestinal, urological, and reproductive tracts. This makes their separation a very challenging task. We report herein pygopagus twins who had minimal fusion in coccygeal region and could be separated without a complicated procedure. The case is being reported to add to the literature and emphasize that simple fusion in conjoined twins can be relatively easy to manage. Copyright:

INTRODUCTION

Conjoined twins are one of the rarest occurrence, with an estimated incidence of about 1 in 200,000 live births and a male-female ratio of 1:3.[12] Pygopagus twins, a rare variant, form 17% of all conjoined twins. They are joined at rump with attachment involving sacrum, buttocks, and perineum.[34] In such pairs, the systems that are likely to be involved are spine, cord structures, bone, genito-urinary and gastrointestinal tract. Difficulty in separation and prognosis depends on the extent of union and neuromuscular involvement. We herein present a pair of pygopagus twins that had minimal fusion at coccygeal region and a good neuromuscular outcome following relatively easy surgical separation.

CASE REPORT

Symmetrical female conjoined twins, born of full-term normal vaginal delivery at a private hospital, presented to us on day 3 of life in stable state. Both were joined together at the lower back and cried immediately after birth. Both had separate normal appearing urinary and anal openings through which urine and meconium was passed with fair sphincteric control [Figure 1]. No neurological deficits were apparent and combined weights of both babies were 4.8 kg. There was a relatively narrow area of fusion at their lower back at coccygeal region with bridge about 3.5 cm long and 1.5 cm wide bearing impression of central “rail track” furrow. Babygram suggested fusion of soft tissues overlying the coccygeal region [Figure 2]. Neurosonogram revealed divergence of posterior elements of lower lumbar and sacral vertebrae in both babies. Magnetic resonance imaging (MRI) of the conjoined twins in the region of the spine and pelvis revealed fusion of the coccyx of both twins with shared dura in this location [Figure 3a-c]. Ultrasound for the kidneys, ureter, and bladder as well as 2-dimensional echocardiography of both babies was normal. After preanesthetic clearance, babies were taken up for surgery.

Figure 1

Plain radiograph showing fusion of soft tissues overlying the coccygeal region

Figure 2

Clinical photograph showing pygopagus twins joined back to back facing away from each other with attachments at the sacrum, buttocks, and perineum with two separate anuses and vaginal openings. Note also the wide area of attachment

Figure 3

T2W sagittal (a), T2W axial (b) and T1W axial (c) Magnetic resonance images reveal fusion in the region of the coccyx of both twins with shared dura in this location

The babies were placed in the lateral position following induction; cruciate incision was given over the skin bridge dorsally to develop skin flaps for both sides to cover up raw area following separation. Dissection was carried deeper and transversely lying muscle bellies were identified within the connecting bridge. Their insertion was traced up to fused coccyx on either side. Fused coccyx was divided with resection of lower most part of coccyx. Minimally communicating thecal sacs with filum terminale were identified within the bridge, divided and suture closed on either side [Figure 4]. Buttressing of the repair of dural sac was done using surrounding soft tissues. Finally, ventral bridge of the skin was also divided. The separated babies were then put in the prone position and muscles ends were sutured to respective coccyx. Skin flaps were mobilized to cover the raw area. Dressing was applied with care to apply barrier between this dressing and anal opening.

Figure 4

Intraoperative photo showing fused coccyx bone and neural tissue in pygopagus twins which are being separated

The babies were started on breast feeds from the postoperative day 1 which they tolerated well. Mild wound infection in the lowermost part was managed well with local dressings and antibiotics orally. No neuromuscular deficit was noted. Both babies discharged on the postoperative day 7 in stable conditions. One baby reportedly developed mild hydrocephalus 1 month postdischarge which got settled over next 6 months with conservative management. At present, both babies are 3 years and 6 months old, are growing well. They are fully continent both for urine and stools.

DISCUSSION

According to the theory of fusion propounded by Spencer, pygopagus twins occur when fusion of babies occur at caudal neuropore.[5] Pygopagus has been classified into five patterns: (1) nonfused rectums and two anal orifices, (2) nonfused rectums with one terminating in a normal anus and the other terminating in a rectovaginal fistula, (3) one nonfused rectum in a viable twin and one incompletely formed intestinal tract with no anus in a nonviable parasite, (4) two colons fused into a common anorectum with a high “Y” junction, and (5) two colons fused into a common anorectum with a low “Y” junction.[34] Our case belongs to the first pattern. Pygopagus are more common in girls and have better survival in females as compared to males.[3] However, girl pygopagus twins generally have fused rectums, whereas in our case and in that reported by Matta et al. separate rectum and colons were seen.[4] This finding makes these cases interesting and led to their relatively easier separation. Another point to heed is that surgical separation of twins was done in the neonatal period itself. Although neonatal period could be high risk for anesthesia and blood loss point of view, a relatively narrow fusion led to our decision of early separation to facilitate nursing care of babies.

Hirokazu et al. reviewed literature of 33 cases of pygopagus. Of these surgical separations was performed in 26 cases, dural sharing was present in 17 cases while spinal cord sharing was present in 10 cases.[6] A high incidence of involvement of spine and neurological tissue between these twins makes MRI, 3 dimensional reconstruction of spine and paraspinal tissues and even neurophysiological mapping essential investigation for planning surgical separation and getting good results. Our set of twins had minimal sharing of a thin dural outpoching which could be easily divided and repaired. However, more complicated procedures as separation of two spinal cord or cord with short nerve roots have also been described, especially in the presence of spinal anomalies.[789] In such cases providing dural cover and support to the repair becomes all the more challenging and such separations are at risk of cerebrospinal fluid (CSF) leaks, infections, and retethering.[910] In our patient, there was limited wound infection, mainly because of proximity of repair to anal orifice. A bigger area of fusion also makes planning of flap, graft or tissue expanders for skin stretching and the latter may be associated with associated complications.[710] Posterior skin wound dehiscence followed by CSF leak was reported after surgery requiring reoperation once or twice.[910]

Few cases of pygopagus required procedures for urethro-vaginal mobilization and reconstruction (with vulvoplasty), rectal mobilization or division of anal canal in midline to achieve normal anal openings and genitalia. In our twins, an inherently good anatomy and attaching transversely lying muscle bellies to either baby's coccyx led to good outcome.

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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

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