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One stage operation through modified posterior sagittal approach for imperforate anus

Nguyen Thanh Liem,
Department of Surgery, National Hospital of Pediatrics, Hanoi, Vietnam




Nguyen Thanh Liem MD, Ph.D
Professor of Pediatric Surgery
National Hospital of Pediatrics
18/ 879 Lathanh Road, Dongda District, Hanoi, Vietnam
Tel: +84 4 3835 7533; Fax: +84 4 3775 4448
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.



Purpose: To describe the surgical technique and preliminary results of a one stage operation through modified posterior sagittal approach (PSAP) for anorectal malformations.

Material and Methods: 66 patients were operated by a one-stage operation through a modified PSAP from January 1998 to November 2005. The operation was performed in one-stage through a posterior sagittal approach with three modifications: The external sphincter complex was not opened on the posterior side, the dissection was carried out outside the rectal pouch and the rectal pouch was not tapered.

Results: There were 57 girls and 9 boys, ranging from 2 days to 12 months of age. The types of anorectal malformations included anal atresia with vestibular fistula in 53 patients, anal atresia with urethral fistula in 7 patients, anal atresia without fistula in 4 patients and anorectal atresia with vaginal fistula in 2 patients. The mean operative time was 68 minutes. There was one death on the fifth postoperative day due to bronchopneumonia and associated heart anomaly. Rectal retraction occurred in two patients and required a second operation. All of the remaining patients could pass stool spontaneously before discharge.

Conclusion: One stage operation through modified PSAP is feasible and safe for anorectal malformations.

Key words: anorectal malformation, modified PSAP, one-stage operation




During the last decade, multi-stage operations through PSAP became the standard procedure for the correction of anorectal malformations [1 - 4]. However a one-stage operation was also used with good results [5 - 8]. Since 1984, a staged operation using a modified PSAP keeping the external sphincter intact was used in our hospital to repair anorectal malformations providing good fecal continence [9]. In order to reduce the cost and time of treatment, since 1998, one stage operation using a modified PSAP keeping the external sphincter intact has been used.

This study reports on a series of 66 cases that were operated on by this technique from January 1998 to November 2005. The aim of this report was to describe technical surgical details and to examine the feasibility, the safety and early outcomes of the technique.

Patient and method

Sixty-six patients were enrolled in this study from January 1998 to December 2004. Only female patients suffering from anal agenesis with vestibular fistula were selected for this procedure. Since January 2005, the technique was applied for all types of anorectal malformations, with the exception of cover anus and patients whose birth weight was less than 2000 gram or who had severe bronchopneumonia.

An invertogram was performed to determine the level of rectal descent in boys and girls, who has no visible fistula. Abdominal and cardiac ultrasounds were carried out to assess renal and cardiac anomalies. Voiding cystography was performed in boys to detect the urethral fistula.

The patient was placed in prone jackknife position. An inverted Y-shaped incision of the cutaneous and subcutaneous planes was made from the coccyx to the anal dimple. From superior aspect, the incision was extended 2-3 cm higher than the level of the coccyx ( fig. 1). The coccyx was removed. The incision was continued until the external sphincter came into view. The midline dissection above the external sphincter was continued to the puborectalis or rectal pouch. Once visualized the puborectalis was retracted downward. The ligament between the rectal pouch and the coccyx was divided. The rectal pouch was detached from the anterior surface of the sacrum using a small peanut dissector. The lateral ligaments were divided freeing the lateral side of the rectal pouch. Separation of the rectal pouch from the urethra or the vagina was achieved by meticulous dissection.

Separation of the rectal pouch from the urethra or vagina was accomplished more easily when the initial dissection was begun near the peritoneal reflection. After the dissector was passed through the rectourethral septum or the rectovaginal septum ( fig. 2), the rectal pouch was retracted posteriorly with a vessel loop. The dissection of the rectum from the urethra or the vagina was continued distally to the fistula. The fistula was divided and closed ( fig. 3). In the case of vestibular fistula, the fistula stump was inverted through the vestibular orifice, and the stump was completely excised to prevent ongoing mucus secretion. The orifice was closed. The dissection between the rectum and urethra or the vagina was continued proximally until the rectal pouch was mobilized and could be pulled through without tension. A neuromuscular stimulator was used to identify the center of the external sphincter, through which a tunnel was created ( fig. 4) and then dilated gradually using Hegar dilators (sizes 6-12).

imperforated anus 1

Fig. 1: Y-shaped cutanous incision

imperforated anus 2

Fig. 2: Dissector was passed through the rectourethral septum

imperforated anus 3

Fig. 3: Fistula was divided

imperforated anus 4

Fig. 4: Tunnel was created through the center of the external sphincter

The rectal pouch was pulled through the tunnel, then sutured to the external sphincter and then to the skin. The rectum was sutured to the upper border of the external sphincter complex by several sutures, then the incision was closed. A 24 F Foley catheter was inserted into the rectum. Colon wash out via this catheter was performed with normal saline until the liquid was clear. The catheter was kept in-situ for 3 days. When the rectal pouch was not identified by PSAP, a tunnel was created through the external sphincter complex and a catheter was placed through this tunnel into the pelvis, and the incision was closed. The patient was moved into supine position. The rectum was freed by laparoscopy or laparotomy and pulled through the tunnel of the external sphincter complex guided by the catheter left in-situ. The new anus was gradually dilated from the 14th postoperative day for a period of one month.


During the study period, 66 children were operated on including nine boys and 57 girls. The age distribution was follows:

  • 1-3 days  - 15 
  • >3 days - 30 days - 9 
  • 1-3 months - 15 
  • > 3 months - 27 

Types of anomalies included:

  • Anal agenesis with rectovestibular fistula 53
  • Anal agenesis without fistula 4
  • Anal agenesis with rectobulbar fistula 5
  • Anorectal agenesis with rectoprostatic fistula 2
  • Anal agenesis with rectovaginal fistula 2 A

Associated malformations occurred in 11 patients: cardiovascular anomalies: 6; urinary tract malformation: 3; sacral malformation: 1; Down syndrome: 1

65 children were operated on by a single PSAP and one by combined laparoscopic - PSAP The operative time ranged from 35 minutes to 120 minutes, average: 68 minutes. One patient died on the 5th postoperative day due to severe bronchopneumonia and associated ventricular septal defect. Complications occurred in five patients: two with rectal retraction (one patient required a colostomy and a repullthrough by PSAP was done in the other) and three with wound infections. The postoperative hospitalization time ranged from 5 days to 15 days (mean: 7 days). All children could pass stool spontaneously before discharge with the exception of one patient requiring a temporary colostomy.

Follow-up was obtained in 18 patients ( from 4 months to 2 years). Anal stenosis occurred in 3 patients who responded to anal dilatation. 14 patients had 1 – 3 defecations per day. 2 patients defecated more than 6 times per day. 2 patients had 1 defecation every two days.


The conventional approach to the surgical treatment of anorectal malformations consists of a diverting colostomy in newborn and, at 3-6 months of age, a definitive pullthrough procedure with subsequent closure of colostomy. This approach was safe, and widely accepted, providing satisfactory results [1 - 4]. However, with advances in anesthesia and resuscitation, definitive surgery can now safely be performed in one-stage. This series supports such a view with a low complication rate: only two rectal retractions required a second operation and three wound infections. Although one patient died in this series, it occurred in the setting of a high risk patient with ventricular septal defect and severe bronchopneumonia.

These results compare favorably with other reported series in which a multistage surgical approach was taken [3,4,9]. There are many advantages of a one-stage operation over the staged operation: (1) Reduce the time and the cost of treatment; (2) Reduce the psychological stress for the family; (3) Avoid complications related to colostomy, which can occur in up to 20% - 40% according to some reports [9,11,12]; (4) Restore early gastrointestinal continuity which, some authors have proposed, could train the perineal musculature and improve fecal continence [6].

One-stage operation can be achieved by different approaches [5 - 10]. Of them, as seen in staged surgery, PSAP is the most popular [6,7,9,10]. In the original PSAP the operative field was rather large, and anorectoplasty could be easily carried out. However the external sphincter was divided completely and closed after the pull through procedure, disrupting the integrity of the sphincter with negative effects on fecal continence. Scarring of the external sphincter could contribute to constipation and is a primary concern with this approach according to different reports [3,4].

Anorectoplasty through modified PSAP keeping the sphincter intact has some advantages. In this operation the sphincter is maximally protected as the external sphincter is not divided and instead the rectal pouch is pulled through a tunnel created in its center. Moreover the integrity of the internal sphincter is preserved because the posterior aspect of the rectal pouch is not opened longitudinally, and the taper is not performed. With maximal preservation of integrity of the external and internal sphincter, we believe that the operation could provide better fecal continence. However a long-term follow-up should be carried out to evaluate the long- term outcomes.

The risk of infection could potentially be reduced because the dissection is carried out outside the rectal pouch. It could also avoid potential breakdown of sutures on the external sphincter when wound infection occurs [10]. The complication rate in our series is similar to other reports using the original PSAP [9,10]. The operation could be applied for most cases of anorectal malformation except form of cloaca. Our study showed that one-stage operation through modified PSAP keeping the sphincter intact is feasible, safe, and achieves good early outcomes.





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