An Incomplete Birth: A Case Report and Literature Review of a Rachipagus Parasitic Twin

Abstract

Parasitic twins are a rare variety of congenital twins. Rachipagus is a type where a partially formed twin is attached to the spine. We present a rachipagus case managed at our institute by a multidisciplinary team. We managed this case with a staged approach. During the first surgery, coil embolization was done for the feeder vessel, followed by parasitic limbs excision, while lipomeningomyelocele (Lipo-MMC) was repaired during the second surgery.

INTRODUCTION

Parasitic twin or heteropagus is defined as a type of asymmetrically conjoined twinning in which the tissues of a severely defective, generally nonviable twin are dependent on the cardiovascular system of its intact counterpart, or “autosite.”[1] Union occurs at homologous sites. The most prominent location of fusion further subdivides these cases. The recognized nomenclature includes 8 such sites: head (cephalopagus), cranium (craniopagus), spine (rachipagus), the chest (thoracopagus), umbilicus (omphalopagus), hip (ischiopagus), buttocks (pygopagus), and spine side (parapagus).[2] Only 2 case series have been published regarding this condition in the literature, including <50 cases of rachipagus.

CASE REPORT

An 8-month-old male infant born term at home by normal vaginal delivery to a multigravida (G5) mother was brought to our center with extra limbs attached to the back of the child. Mother had an uneventful antenatal period with normal antenatal ultrasounds, according to her, but actual documents were not available. The parents complained of additional limbs and swelling at the back [Figure 1a and b], with inability to sit and roll over. The patient passes urine in a stream with in between dribbling episodes. On examination, the child was healthy, and there was a parasitic twin attached to the sacral region, which contained nonfunctional lower half of the parasite (two lower limbs and an appendage), bifid scrotum and penoscrotal transposition, displaced anal opening of autosite to the right, lipomeningomyelocele (Lipo-MMC), and left foot congenital talipes equinovarus (CTEV) in autosite. Detailed evaluation of the child revealed a single right kidney with Grade III vesicoureteric reflux (VUR), 3 mm ventricular septal defect (VSD), and Lipo-MMC with noncommunicating hydrocephalus. Computed tomography (CT) angiography showed the parasitic twin getting blood supply from the autosite’s left internal iliac artery via the left internal pudendal artery [Figure 1c and d, white arrow]. CT revealed an extra pair of pelvic bones with two hip joints on each side separated by 6 mm distance, and a pair of lower limbs on each side of the parasitic twin. A rudimentary kidney was present at the junction between the autosite and parasite [Figure 1c, red arrow], which was draining into the urethra of the autosite. The rest of the abdominal organs were reported to be normal. Dimercaptosuccinic acid (DMSA) scan revealed a single right kidney with normal cortical function with no evidence of scar. The estimated GFR of the patient was 169 ml/min/1.73 m².

Figure 1.

Preoperative images of the rachipagus baby (a). Semilateral view of the patient with additional lower limbs with appendage, bifid scrotum, and deviation of anal opening to the right (blue arrow); (b). Prone position of the child demonstrating the lumbosacral MMC and extra lower limbs and appendage in between; (c). Right oblique view of 3D CT reconstruction of parasitic twin showing relation between the two hip bones, rudimentary kidney (red arrow) at junction of parasite and autosite, and feeder vessel for parasite twin from left pudendal artery of left internal iliac (white arrow); (d). Anterior view of 3D CT reconstruction showing feeder vessel for parasitic (white arrow)

A multidisciplinary meeting was held, consisting of interventional radiologists, pediatric surgeons, neurosurgeons, plastic surgeons, orthopedics, cardiothoracic surgeons, and an anesthesiologist, wherein the decision to stage the surgeries and to coil the feeder vessel to minimize blood loss was planned. Parents were counseled regarding the same, and after their consent, surgery was carried out.

In the initial surgery, coil embolization was done for the feeder vessel by the intervention radiology team through the right femoral artery. The parasitic twin was then excised by a multidisciplinary team. Postembolization skin discoloration was noted in the parasitic limbs, and skin incision was planned such that the majority of closure would be provided by the superiorly based flap based on lumbar perforators. Both parasitic lower limbs were disarticulated from the hip joint, following which the bony pelvis was separated from the autosite. Vascular pedicle was identified and doubly ligated, and rudimentary kidney was preserved. Closure was done in layers, and adequate flap coverage was provided. The patient developed discoloration with cold and feeble pulse in the right lower limb of the autosite immediately after surgery, for which USG Doppler was done, which showed thrombus in the right femoral artery, and urgent open thrombectomy was done.

The patient was kept on elective mechanical ventilation in intensive care and was subsequently extubated on postoperative day (POD) 1. The wound got contaminated due to fecal soiling, which later dehisced. The patient was taken for diversion colostomy with wound debridement and closure. The patient then had an uneventful postoperative course and was discharged on POD 15.

The patient is now able to sit without support [Figure 2a], stand with support and roll over, and have normal lower limb movements and healthy scar at the back [Figure 2b and c]. Lipo-MMC repair was done by the neurosurgery team after 9 months, following which the child had an uneventful postoperative course. The patient will be planned for colostomy closure at later date. On 1-year follow-up, the patient is doing well on uroprophylaxis without urinary tract infection, has persistent Grade III VUR in the right kidney in repeat MCU, and preserved cortical function on repeat DMSA scan.

Figure 2.

Present status of child – (a) able to sit without support, (b) postoperative scar, (c) postoperative anal area

DISCUSSION

The embryogenesis of the heteropagus spectrum constitutes a continuum, and they represent variations of abnormal conjoined twinning, characterized by the site of union and the extent of damage to the parasite.[3]

The most common abnormalities in the autosite in rachipagus involve the CNS and vertebral column, usually close to the site of union, and interestingly, other significant abnormalities in autosites are rare. These seem to be more common in cases with extensive union, both of whom showed malformations of the cloacal membrane and lower genitourinary and alimentary tracts. A single right kidney with Grade III VUR was found in our patient. Parasites can be associated with a segmented spine, ribs, scapula, clavicle, and accessory or dysmorphic lower extremities, rudimentary hemipelvis, or external genitalia.[1]

In previously reported cases of rachipagus, the authors have mentioned the attachments of the rachipagus PT to the spinal cord and highlighted the difficulty as well as the importance of untethering and proper dissection of neural elements.[4]

Similarly, two cases of rachipagus were reported, wherein the blood supply was arising directly from the aorta.[5] One should therefore be very careful during dissection, as injury to major vessels can be catastrophic. Second, before ligation of a vessel, one must ensure that it is supplying only the parasite and not any vital autosite structure. In our case, we preoperatively identified feeder vessel, which was coil embolized before surgery.

As literature mentions, surgery (removal of the parasitic twin) is curative for most autosites. Surgical procedures are usually elective, but emergency surgery is indicated when there is bleeding from the mass. Nontreatment may lead to neurological deficits like paraparesis or bladder and bowel incontinence.[6] Hence, surgery may not be postponed for a long time.

Complicated cases may require a staged approach for separating the parasite and dealing with associated anomalies.[7] We resorted to the staged approach and postponed dealing with the Lipo-MMC until a later date.

These children require long-term follow-up, which may even necessitate surgeries on anatomical cosmetic reconstructions, associated urinary anomalies, urinary and fecal continence, and occurrence of detethering of the cord.

CONCLUSION

Rachipagus is an uncommon variant of parasitic twin. Surgical challenges vary accordingly and require a multidisciplinary approach for optimal management. Prognosis can be affected by the excellence of anatomical restoration. Proper preoperative evaluation and postoperative care, as well as adequate follow-up are beneficial for long-term satisfactory outcomes.

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.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.