A 34-year-old woman, who conceived via in vitro fertilization, received the diagnosis following fetal ultrasound screening at 11 weeks and confirmed by magnetic resornance image (MRI) at 16 weeks of pregnancy. The images revealed the connection between the sacrum and a continuous spinal canal; however, they had separate intra-abdominal organs.
Twins with male pygopagus were born at 35 weeks by cesarean section, with a combined birth weight of 4690 g. At birth, the infants had no signs of distress. They shared one anus, one penis, and one scrotum with four testes (Fig. 1a–d, respectively). Defecation and urination after birth were normal. MRI showed that the twins had a fused sacrum, and their spinal cords shared one continuous tube (Fig. 2a). They had a short common anus and rectum (Fig. 2b). Computed tomography (CT) revealed two bladders, rectums, livers, and spleens (Fig. 2c). Additional evaluation of urinary tract showed that twin A had horseshoe kidney and twin B had unilateral vesicoureteral reflux (grade 3). Separation was scheduled when the infants were 5 months. The surgery aimed to separate the sacrum, spinal canal, fused rectum, fused penis, and scrotum while preserving their functions.
Two different anesthesia teams and four surgical teams (neurosurgery, pediatric urology, plastic surgery, and pediatric surgery) were involved. Detailed surgical procedures were discussed twice using a preoperative 3D model (Fig. 2d).
In the operating room, the twins were first intubated, and central venous catheters were inserted by the respective anesthesiologists. The placement of the anesthetic instruments was designed to enable preparation for intraoperative repositioning and post-separation position, as reported in detail by Sato et al. [9]. Urinary catheters were placed into each twin’s bladder using cystourethrography under general anesthesia. Each bladder was not trabeculated, and bladder neck was closed. Common urethra was not wide and extended to the external urethral meatus. We planned the separation beginning from the superior organ toward the inferior organ to avoid contamination due to rectal and penis separation.
The patients were placed in the prone position. After the sacrum was separated, a fused nerve root was confirmed within the spinal canal (Fig. 3a). Neurosurgeons separated the fused spinal cord and nerve roots using microscopy and neuro-physical intraoperative monitoring and repaired the dura mater. Details of the surgical separation of conjoined spinal cords of this case have been reported by Yokota et al. [10]. After spinal cord separation, we detected the fusion of the two rectums near the anal aperture (Fig. 3b). Their sphincters and puborectalis were partially shared; therefore, they were separated using an anal stimulator with keen attention to their morphology. Similarly, the fused penises and urethra were separated (Fig. 3c). Four cavernous bodies were detected in the fused penis, which were divided into two pairs of bodies. The pendulous urethrae were separated equally between both infants and peeled off to the bifurcation of the bulbar urethrae. After confirming that the spermatic cords of both infants were not crossed, the scrotums were separated at the same incision line as the skin. Each perineal urethrostomy was created, because each separated urethra was not wide enough to perform single stage urethroplasty. The urethral plate and penile skin were sutured with Byar’s flap to wrap the penises. The scrotums were reconstructed with the Dartos fascia, and the skin was closed (Fig. 3d). The dissected rectum and anal canal were reconstructed to pass through the sphincter and puborectalis (Fig. 3e). The position of the neo-anus was detected and placed on the separation line using a muscle stimulator. Finally, a transverse colostomy was performed to cover the anus.
Both patients had an uneventful postoperative course. They had no motor dysfunction of the lower limb and no obvious urinary incontinence, and they underwent a stoma closure surgery 4 months later. Nine months later, they underwent tubularized incised plate urethroplasty for hypospadias. Eighteen months after separation, both children could walk alone (Fig. 4a). The scars were clear, without complications (Fig. 4b), and external urethral orifices and anal apertures were confirmed (Fig. 4c). They had bowel movements once daily by enema without soiling. They voided spontaneously without urinary incontinence at the time of 3 years and 11 months.
