Stricture rate in patients after the repair of anorectal malformation following a standardized dilation protocol

The aim of this study was to determine and analyze the stricture rate in patients who underwent a PSARP or PSARVUP and followed a postoperative protocol of anal dilation (Fig. 1). A retrospective review of patients with anorectal malformation (ARM) who underwent a primary PSARP or PSARVUP from February 2016 to October 2021 was performed. Data collected included patients’ demographics, type of ARM, age at the time of operation, postoperative complications, with emphasis on whether there were any strictures or any difficulties during dilations, and on follow-up. During the surgical repair, emphasis was placed on preserving the blood supply of the bowel and performing a tension-free bowel-to-skin anastomosis. Eighty-four patients met the inclusion criteria. Forty-four patients were females: 21 recto-perineal fistula, 12 cloaca, 9 recto-vestibular fistula, one imperforate anus without fistula, and one patient had a complex anorectal and vaginal malformation with an anal stricture and a rectovaginal fistula. Forty patients were males: 14 recto-perineal fistula, 11 recto-urethral bulbar fistula, 6 recto-urethral prostatic fistula, 6 imperforate anus without fistula, and 2 bladder neck fistula. One patient had an anal stenosis with sacral agenesis, without a presacral mass. Patient ages ranged from 0 to 79 months (mean 7.5 months, median 5 months) at the time of surgery. Follow-up time ranged from 7 to 73 months (mean 38 months, median 35 months). No patient suffered of a postoperative anal stricture. Six patients suffered of a rectal prolapse that required a surgical repair. Post-operative anal stricture after PSARP and PSARVUP can be avoided with proper surgical technique and postoperative care. Namely, by preserving adequate blood supply of the bowel and avoiding tension at the anoplasty, and by adhering to a structured protocol of anal dilations.


Introduction
Postoperative anal dilations are standard treatment since the early introduction of the posterior sagittal anorectoplasty procedure (PSARP) for children born with an anorectal malformation (ARM) [1]. Postoperative anal dilations are performed by over 80% of the pediatric surgeons [2] following a variety of protocols based on their personal preferences. In our practice, parents are taught how to perform anal dilations on their children 14 days after surgery. We start with a small Hegar dilator (8-9 mm), and advise the parents to increase the diameter every week, until they reach a predetermined diameter based on the patient's age, when parents will then start the tapering phase of the protocol (Fig. 1). Recently, we were surprised to read reports in the literature about stricture rates as high as 26% following a PSARP, with some 22% of cases requiring further surgical intervention for stricture repair, [3]; with or without following a postoperative protocol of anal dilations. We aimed to analyze our stricture rate after PSARP and PSARVUP following our standardized protocol of anal dilations, in part because some surgeons believe that anal dilations are not necessary and that dilations produce severe pain and may result in significant psychological sequelae [4].

Methods
A retrospective review of all patients with anorectal malformation (ARM) who underwent a primary PSARP or PSARVUP at our institution from February 2016 to October 2021 was conducted, with patient follow ups until April 2022 included in the review. All included patients followed our postoperative anal dilation protocol (Fig. 1). Patients were evaluated for presence of anal stricture at the time they reached the final Hegar size number (predetermined based on the patient's age), and at the oneyear follow-up clinical visit. Colorado Multiple Institutional Review Board (COMIRB) approval was obtained (COMIRB #22-0428). Data collected included patients' demographics, type of ARM, age at the time of operation, postoperative complications, with an emphasis on the presence or absence of stricture, difficulties noted during dilations, and follow-up. During the surgical repair, emphasis was placed on preserving the blood supply of the bowel and on performing a tension-free bowel-to-skin anastomosis.

Results
Eighty-four patients underwent a PSARP or PSARVUP due to anorectal malformation at our institution and followed our postoperative anal dilation protocol. Patient ages ranged from 0 to 79 months (mean 7.5 months, median 5 months) at the time of surgery. Follow-up time ranged from 7 to 73 months (mean 38 months, median 35 months). Dilations are initiated in the clinic, 14 days after PSARP or PSARVUP, during an instructional session for the parents during which they learn how to perform subsequent dilations at home Forty-four (52%) patients were females. Twenty-one of them had a recto-perineal fistula. Twelve had a cloacal anomaly (8 had a common channel < 2.5 cm and 4 had a common channel > 3.5 cm). Nine had a recto-vestibular fistula and one with trisomy 21 had an imperforate anus without fistula. One patient had a complex anorectal and vaginal malformation with anal stenosis and a rectovaginal fistula.
Forty patients were males (48%). Fourteen had an ARM with a recto-perineal fistula, 11 had a recto-urethral bulbar fistula, and 6 had a recto-urethral prostatic fistula. Six had an imperforate anus without fistula (3 of which had trisomy 21), and two had an ARM with a recto-bladder neck fistula. One patient had an anal stenosis with sacral agenesis, without a presacral mass.
When asked about pain, suffering or discomfort experienced during dilations, parents described that most children manifested some discomfort but no real pain. Most parents were anxious prior to the first dilation.
None of the 84 patients suffered from postoperative anal stricture, and all patients reached the final Hegar size, as determined by their ages, without any problems. Eighty-one patients had no stricture at the 1-year follow-up. The remaining three patients have not yet had their 1-year follow-up as of the time of this submission.
Six patients, two female and four male patients, suffered from rectal prolapse postoperatively and required surgical intervention (Table 1). Rectal prolapse repair was performed within 2-12 months after the PSARP procedure.

Discussion
The need for anal dilations after a PSARP has been debated recently in the literature [3,[5][6][7]. We speculate that when anoplasties are performed without respecting the limits of the sphincter, or in patients without a sphincter, then the result is a large, patulous anal orifice, somewhat resembling a colostomy. These particular patients do not need dilations as they will never develop strictures (Fig. 2).
On the other hand, when the limits of the sphincter are respected, the anus is visibly closed at the end of the operation due to the existing sphincter muscle tone (Fig. 3).
In this scenario, if dilations are not performed in then this patient will most likely develop a ring-like stricture at the skin level. We also think that painful, forceful, traumatic anal dilations occur in patients who underwent anoplasties with poorly perfused or even ischemic bowel and (or) were created under undue tension. Those patients will develop severe anal strictures which are almost impossible to dilate. In these cases, the pain caused by the dilations may be so severe that some surgeons opt to perform them under anesthesia every one or two weeks. This kind of management results in some of the most severe, fibrotic strictures that eventually require a re-operation.
Based on our experience, we believe that performing a technically correct anoplasty, preserving adequate blood supply to the bowel, avoiding undue tension on the bowel-toskin anastomosis, and respecting the limits of the sphincter, will make regular anal dilations a painless experience with no suffering and only minimal discomfort.
We do observe parental anxiety when they are guided on how to do anal dilations for the first time. However, afterwards many of them have expressed their relief at seeing that the experience was not nearly as bad as they had imagined it to be, and they leave our clinic confident in the ability to perform subsequent dilations at home. In this cohort, most patients were younger than 6 months of age at the time of their PSARP. We acknowledge that trying to perform anal dilations in toddlers or older children should be discouraged, and this is one of the reasons why we prefer to do the PSARP at a young age.
The rate of rectal prolapse requiring surgical intervention in this study population was 7% and in the literature its occurrence ranges from 3.8% up to 27% [3,[8][9][10]. The incidence of rectal prolapse is important to mention when evaluating skin-level strictures after a PSARP and when debating the need for postoperative anal dilations. When rectal mucosal tissue is left exposed and is visible immediately after the conclusion of the PSARP, then the patient will have no risk for stricture at the muco-cutaneous junction. However, we advise against this practice as a means of preventing strictures because prolapsed mucosa has other inconveniences.
We acknowledge the limitations of this study due to it being both retrospective and non-randomized. Because of this, we cannot isolate the impact of the surgical technique versus the impact of the postoperative anal dilations in the incidence of postoperative strictures reported in this series.

Conclusion
Postoperative anal strictures after PSARP and PSARVUP can be avoided with a technically correct operation that emphasizes the preservation of adequate blood supply to the bowel and an anoplasty fashioned without tension, and a follow-up plan consisting of a structured (standardized) protocol of anal dilations.