Incidentally found rectal duplication during surgery for rectovestibular fistula and its management.

Association of rectal duplication with rectovestibular fistula is rare. A 3-month-old patient underwent primary posterior sagittal anorectoplasty (PSARP) for rectovestibular fistula. During surgery the patient was found to have a rectal duplication (RD). We managed the case by excising the common wall and fenestrating the two lumens together and completed the PSARP.

INTRODUCTION

Gastrointestinal tract duplications are rare and mostly occur in ileum, with only 5% of all duplications occurring in rectum.[1] There have been about 17 case reports of hindgut duplication associated with anorectal malformation (ARM) of which 8 are rectal duplications.[12345678] We are reporting a case of rectovestibular fistula incidentally found to be associated with rectal duplication during surgery. To the best of our knowledge this is the first case report of rectal duplication associated with rectovestibular fistula being treated by fenestrating the two lumens together.

CASE REPORT

A 3-month-old female child presented to us with history of passing stools from an abnormal opening in the vestibule. On clinical examination she had a rectovestibular fistula with normal sacrum and rounded gluteal folds consistent with low ARM. USG abdomen and pelvis was normal. She was scheduled for primary PSARP at 3 months of age. Intraoperatively after opening the sphincter muscle and mobilizing the rectum and completing the anoplasty when Hegar dilator was passed it was stopping short 8 cm in a blind pouch. Hence, sutures were removed and on careful examination we identified two openings in rectum [Figure 1]. One was a blind ending pouch posteriorly about 7 cm long situated 3cm above anal verge. The other opening was continuous with sigmoid [Figure 2]. As the rectal duplication was 3 cm above the anal verge we were not able to identify it before. The common wall was excised, the two coli anastomosed and PSARP completed. Histopathology of the common wall confirmed rectal duplication with no gastric mucosa.

Figure 1

Rectal duplication (Type II B) intimately fused with rectum and associated with rectovestibular fistula

Figure 2

Schematic diagram of the rectal duplication with anorectal malformation

DISCUSSION

Rectal duplications are rare congenital anomalies forming less than 5% of alimentary tract duplications. Various embryological theories have been explained from pinching off of diverticula to caudal twinning and disordered separation of endoderm from notochord. Rectal duplication associated with ARM can present as Currarino's triad with presacral mass and sacral anomalies. They can be cystic (type I) and tubular (type II). Most of the rectal duplications are cystic and 90% do not communicate with the rectum.[1] Our patient had rectal duplication which was tubular and was communicating with the rectum (type II B), which is very rare.

There are only about eight case reports of rectal duplications associated with ARM described in literature. Most of these were managed by excision of the duplication [Table 1]. But our patient was managed by excision of common wall and fenestrating the two lumens by side to side anastomosis in its entire length.

Table 1

Summary of reported cases of rectal duplication associated with anorectal malformation

There have been reports of rectal duplication being missed in low ARM and diagnosed later when patient came back with constipation.[4] In our case we would have missed the rectal duplication since it was intimately fused with rectum having a common muscularis wall and opening higher up in rectum. Being alert while dealing with these complex malformations is essential. Optimal treatment described for rectal duplication is total resection when feasible (for fear of ectopic gastric mucosa if present causing ulceration and malignant degeneration), mucosal stripping and fenestrating the two lumens together when there are important adjacent structures.

There is no standard treatment for duplications incidentally detected during ARM surgery as it is rare. In long tubular duplications of hindgut, resection of the duplication would require a subtotal colectomy due to shared blood supply, and this is not usually a desirable option in small children. Rectal duplication associated with ARM especially if intimately fused would require an extensive resection of rectum which would compromise on continence. So alternatively in these complex cases a variety of other approaches may be required like mucosal stripping or fenestrating the two lumens by linear stapler or hand sewn side to side anastomosis.[19]

In our patient the rectum was intimately fused with the duplication and it could not be excised separately. Excision of both coli together would require an extensive abdominoperineal approach sacrificing the rectum and pulling the sigmoid as neoanus. The common wall was thin and child was completely asymptomatic in terms of clinical presentations for rectal duplication with normal sacrum. So we decided to excise the common wall and anastomose the two coli together. The surgical procedure should not be more radical than necessary to eliminate the patients complaint and prevent further recurrence.[10] The child is on close follow up and has attained fair continence.Tc99 scan done to rule out any ectopic gastric mucosa does not show any abnormal uptake in rectum.

We conclude that although the occurrence of rectal duplication with ARM is rare and surgical excision is the preferred treatment, in complex cases where tubular rectal duplication is intimately fused and has a common muscularis wall, fenestrating the two coli is also a surgical option which is more conservative preserving the anorectal function.