Surgical Surprise during Posterior Sagittal Anorectoplasy: A Rectal Duplication.

An 8-month-old boy with anorectal malformation (ARM) was incidentally found to have double rectal pouches during posterior sagittal anorectoplasty. The distal blind-ending pouch was excised, and the larger proximal pouch was tapered and anorectoplasty performed. The excised pouch was confirmed as rectal duplication cyst. One must be aware of such uncommon associations with ARM.

INTRODUCTION

Anorectal malformations (ARMs) are commonly associated with multiple congenital anomalies; however, the association of ARM with rectal duplication (RD) has seldom been reported. RD is an extremely rare congenital malformation with <100 cases reported.[1] Usually asymptomatic, patients with RD may have varied clinical presentations. An unusual presentation of a boy with ARM associated with RD discovered incidentally during surgery has been described in detail. Although such an association has been reported previously,[2] this is probably the first case report on incidentally detected cystic RD with ARM with sacral agenesis and superior vesical fissure in a male child.

CASE REPORT

An 8-month-old baby boy weighing 5700 g presented with a history of absent anal opening and continuous dribbling of urine from the lower abdomen since birth. He underwent high sigmoid loop colostomy at day 3 of life for ARM. On presentation, his abdomen was not distended and a superior vesical fissure was seen in the lower abdominal wall. He was decompressing well from the colostomy. The perineum was poorly developed with flat gluteal folds and the sacrum was impalpable. External genitalia were normal male-like and bilateral testes were descended.

A pressure augmented, distal colostogram showed anorectal atresia with a radiolucent separation, no identifiable rectourinary fistula, and sacral agenesis. The distal length of sigmoid colon seemed adequate to attempt a posterior sagittal anorectoplasty (PSARP). The preoperative echocardiography and renal ultrasound were normal. There was no associated limb anomaly.

The child was taken-up for PSARP with the provisional diagnosis of high ARM with sacral agenesis and superior vesical fissure.

The standard PSARP incision was given, and the muscles were cut and deepened in layers. The perirectal sheath was entered till the shiny rectal pouch serosal layer was reached. Stay sutures were taken on the rectal pouch, adequate lateral mobilization was done, and the pouch was opened in midline for submucosal dissection and anterior mobilization. Another compressible cystic structure was seen superolateral to the previous pouch. Both pouches were opened and were seen to be communicating with one another through a narrow opening, rest being separated by a thick septum. Both were mucosa lined [Figure 1]. The blind ending smaller pouch was completely excised and sent for histology. The second, proximal pouch was mobilized adequately, pulled down, and tapered, and anorectoplasty was completed.

Figure 1

(a) Both the distal and the proximal rectal pouches have been opened after taking stay sutures. (b) The cystic rectal duplication (marked with stay sutures) seen communicating with the dilated, mobilized proximal normal rectal pouch, and descending colon during posterior sagittal anorectoplasty

The child was discharged on the 5th postoperative day on full oral feeds and no surgical site complications. The histopathology confirmed the distal excised pouch as a RD cyst. Three months later, he underwent colostomy closure and subsequently repair of the superior vesical fissure. At the last follow-up at 6 years of age, he is doing well on bowel management program for fecal incontinence and urotherapy and medical management for neurogenic bladder.

DISCUSSION

The association of RD with ARM has seldom been reported.[2345] The diagnosis of RD is based on the criteria by Ladd and Gross: (1) continuity or contiguity with the rectum, (2) presence of smooth muscle tissue in two layers, and (3) a mucosal lining normally present in the gut of that region.[5] In our case too, histology confirmed the diagnosis of RD cyst. RD may be cystic or tubular type and can be positioned anterior or posterior in relation to the normal rectum.[1] Cystic variety is more common and in 90% cases does not communicate with the normal rectum. They show a female preponderance. Ours was an extremely rare case of a posterior, cystic, communicating variety of RD associated with ARM (anorectal agenesis without fistula), sacral agenesis, and superior vesical fissure discovered incidentally during PSARP.

Embryologically duplications arise due to one of the theories: (1) the partial twinning theory, (2) the split notochord theory by Bentley which states that during the 3rd–4th week of gestation, when the notochord starts separating from the endodermal cells, gaps may appear in the notochord through which endodermal cells can herniate and form diverticula, (3) the canalization defects theory where defects in vacuolization of solid organs results in diverticula formation, and (4) the environmental factors theory that suggests stress, hypoxia, and trauma may induce duplications. Our case of RD with ARM may be well explained by the split notochord theory due to the associated vertebral defect.[5]

RDs are mostly asymptomatic and diagnosed late. RDs usually have an external orifice.[2] They may present early as rectal masses, fistulae, or due to compressive symptoms such as constipation, lower back pain, intestinal obstruction, dysuria, suprapubic pain, and urinary retention or with infection or with bleeding through anus due to ectopic gastric mucosa. The timely diagnosis in our case is attributed to the associated ARM.

An abdominal X-ray, ultrasound, computed tomography scan, and magnetic resonance imaging help in diagnosis and localization of these duplications. An anterior sacral meningocele, teratoma, dermoid cyst, and chordoma may mimic cystic RD on imaging. The intraoperative findings and the histopathology proved confirmatory in our case.

Complete surgical excision of duplication cysts is necessary to treat symptoms and avoid infective complications or consequences of ectopic mucosa. The surgery depends on the site, and the size of the cyst and the associated anomalies. In our case, the PSARP approach proved feasible as the perineum was poorly developed, sacrum was absent, and there was adequate length of colon left distal to the colostomy. Pampal et al.[3] reported two cases of RDs with rectovestibular fistulae discovered during the PSARP approach. The abdomino-perineal route has also been described.[4] The latter is beneficial where the cyst is large, or is entering the abdomen, or there are associated genitourinary malformations. The other approaches include transanal and transcoccygeal (Kraske's) approach.[3]

CONCLUSION

ARM can be associated with various other congenital malformations, but its association with RD is rare

Awareness of such an association is necessary lest one may miss the diagnosis in case it presents as a chance finding during surgery like in our case

Histopathology is confirmatory

The posterior sagittal approach is useful only when the distal colon length is adequate, and the tip of the loop can be seen below the last ossified sacral piece on a pressure augmented distal colostomgram.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient's parent has given his consent for his images and other clinical information to be reported in the journal. The patient's parent understands that his names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.