I. Pena procedure Pena procedure is currently the preferred procedure for the staged treatment of high grade anal atresia in three stages: colostomy-anal formation-closure of the fistula. In children with high congenital anal atresia, the proximal sigmoid colon or the junction with the descending colon is fistulotomized through an arcuate incision in the left lower abdomen via the McDonald’s point, and the colon is freed and a double-port fistula is performed on the abdominal wall, as the rectum is estimated to drag out without difficulty in freeing the sigmoid colon. Anoplasty was performed 2-3 months after surgery. Anal dilation was given 2 weeks after the anoplasty. Pena anoplasty is a posterior sagittal approach to anorectoplasty based on the local anatomical features of rectoanal malformation: the external anal sphincter is the main muscle group controlling defecation, which is fused with each other near the normal anus to form a component of the external sphincter complex. This muscle forms a parietal ring around the rectum with the deeper external sphincter muscle groups. (1) All children with rectoanal malformation, including those with moderate-to-high anus, can have well-developed external anal sphincter; (2) The important neurovascularity on the posterior side of the rectum usually does not exceed the midline, therefore, the posterior median longitudinal incision causes the least neurovascular damage; (3) The posterior sagittal approach through the longitudinal incision provides good exposure of the blind end of the rectum and external sphincter, and the anatomical relationship is clear, so that the external sphincter can be separated and performed under direct vision. (4) Most high anorectal deformities have no internal anal sphincter, and the degree of internal sphincter development is related to the type of deformity, i.e., the higher the position, the worse the development, or even the complete absence of the fistula. In intermediate anorectal deformity, the thickened portion of the blind end of the rectum may be the internal sphincter, and in high anorectal deformity, there may be internal sphincter-like changes around the fistula, which should be preserved as much as possible. Therefore, it is important to preserve the structures of the distal rectum during the rectal tow-out procedure. These residual internal sphincters or muscle-like tissues play an important role in keeping the anus closed and preventing fecal overflow after surgery; (5) A sigmoid stoma should be made before or at the same time as the Pena procedure to ensure smooth recovery of the reconstructed anus without stool and to minimize contamination; (6) An electrical stimulator should be used intraoperatively to determine the placement of the rectum in the center of the muscle complex under the guidance of electrical stimulation and to ensure that the sutures are closed according to (6) Always use an electrical stimulator during surgery to determine the placement of the rectum in the center of the muscle complex under the guidance of electrical stimulation, and to ensure that the sutures are closed at the same level. It has been reported in several papers that in addition to repairing the posterior rectal fibers, attention should also be paid to repairing the anterior fibers of the external sphincter complex, which plays an important role in defecation control. If the external sphincter complex cannot completely wrap around the rectum, it can only be fixed on both sides of the rectal wall, not forcibly sutured, in order to avoid stenosis. The main method of first-stage anoplasty is to perform the surgery under general anesthesia with tracheal intubation, and the catheter is routinely placed in the prone position. “The longitudinal incision in the sacral area should be made sequentially through the skin and subcutaneous tissues to avoid injury to the external anal sphincter fibers, and the parsagittal fibers and anal levator muscle should be incised under the guidance of the electrical stimulator. After finding the end of the rectum, several stitches of silk are placed obliquely on the posterior, lateral and anterior walls to facilitate traction, and then the rectum is separated by needle-like electric knife in the submucosa of the rectum, sometimes above the peritoneal reflex, and if there is a urethral fistula, the fistula in the anterior wall can be treated at the same time, so that the free rectum can be passed under the anal sphincter complex and dragged to the anus under tension-free conditions. The anastomosis is performed by making the aforementioned incision at the anal cavity and leaving a gap of approximately 1 cm in length. The skin, subcutaneous tissue, and subcutaneous muscle fibers of the external anal sphincter are also incised sequentially, and a tunnel is made through the middle of the transverse muscle complex under the guidance of an electrical stimulator. If the rectum wall is dilated and hypertrophied, caudal trimming and shaping can be done at the distal end of the rectum to facilitate passage through the tunnel, and then the transverse muscle complex is repaired, paying attention to repairing the posterior fibers of the rectum and the anterior fibers of the external sphincter complex, fixing the rectum and the superficial layer of the anal sphincter, etc. The sacral incision is sutured to the anal raphe, and the incision is closed after complete hemostasis. After the operation, a Vaseline gauze wrapped anal canal is placed through the anus as a rectal stent.