Optimizing Surgical Techniques for Anal Canal Duplications in 2 Pediatric Patients

Introduction

Anal canal duplication (ACD) stands out as the rarest variant among alimentary tract duplications in children [1]. Typically diagnosed before the age of 2 years due to the presence of an extra perineal opening, they are most commonly asymptomatic. While some patients are asymptomatic, others experience nonspecific symptoms, such as abdominal pain, perianal pain, and constipation. In complicated cases, symptoms may include mucous drainage and recurrent fistula. Computed tomography (CT) or magnetic resonance imaging (MRI) is typically performed to accurately define the anatomical location, assess the relationship with surrounding structures, and rule out the presence of presacral masses. Surgical resection is the mainstay of therapy due to the potential for recurrence of infection and malignant transformation [2]. Several techniques have been proposed, tailored to the positional features of the cyst, including trans-anal excision, posterior sagittal, transcoccygeal approaches, and a combined abdominoperineal approach [3]. The final diagnosis of ACD is confirmed through histological assessment, which typically reveals a composition of 3 types of epithelia: squamous, transitional, and columnar [4]. This report presents 2 cases with distinct clinical manifestations and surgical treatments based on their differing localizations.

Case Reports

CASE #1:

A previously healthy 10-year-old girl (weight 40 kg) presented to the emergency department with fever and sacrococcygeal pain. Upon evaluation, ultrasound examination showed a large abscess measuring 8×4 cm in the right ischiorectal fossa, prompting drainage through an endorectal incision and intravenous antibiotics administration (1 gram amoxicillin+clavulanic acid). Although the fever resolved and bacterial wound and blood cultures (aerobic and anaerobic) returned negative results, persistence of exudate from the lesion prompted further investigation. A subsequent MRI and colonoscopy exposed a narrow fistula extending from a large abscess in the ischiorectal fossa to the mid-third of the anal canal, leading to suspicion of ACD (Figure 1). The MRI was negative for presacral masses or other spinal malformations. With this preoperative imaging, the patient was referred to our attention and the case was discussed in a multidisciplinary manner among gynecologists, pediatricians, and radiologists. The clinical evaluation proceeded with a perineal assessment under sedation, and a simultaneous fistulography that confirmed the presence of an accessory opening below the pectin line that connected the abscess in the right ischiorectal area. A tubular drainage catheter was then inserted into the cavity under the guidance of a metal wire, successfully controlling the infection. Due to the presence of this accessory opening, a muscle complex-saving posterior sagittal approach (MCS-PS) was performed (Figure 2) with the patient placed in prone position. The fistulous opening was isolated and divided using traction sutures. The levator muscle was divided vertically above the level of the muscle complex, which was kept intact. With the help of a drainage catheter, the cyst was accessed in its retro-rectal portion and isolated from the rectum, to which it was firmly adhered. The mass was dissected completely from the rectum and the small communication opening was demonstrated between the cyst and the rectum, which was closed by PDS 5/0 suture. A terminal colostomy was also performed, and because the postoperative course was uneventful, the patient underwent stoma closure 4 months later without complications. The pathology report confirmed the suspicion of the anal duplication, showing a mixture of goblet cells, columnar-squamous epithelial cells in the cranial end of the specimen, and squamous epithelium in the caudal end. After 3 years the patient has been asymptomatic with normal anorectal function.

CASE #2:

A 16-year-old girl (weight 50 kg) was referred to our center following the incidental finding of a large ischiorectal cyst discovered during a routine gynecological evaluation. She was otherwise in good health and had not undergone any previous treatments for medical conditions. A preoperative pelvic MRI revealed a well-defined homogeneous cystic mass measuring 7.3×6.3 cm in the left ischiorectal fossa in continuity with the rectal wall (Figure 3). No other sacral or spinal abnormalities were found. Subsequent rectoscopy and trans-anal ultrasonography confirmed the cystic nature of the mass without an apparent external opening. This case was discussed in a multidisciplinary manner, prompting a decision to use a robot-assisted surgical approach, considering the absence of an external orifice. Surgical access was gained with a supraumbilical 8-mm camera port followed by 2 other 8-mm ports on the transversal umbilical line. The abdomen was insufflated to an abdominal pressure of 10 mmHg with C02 supplied by the Air Seal Flow System. Intraoperative colonoscopy aided the cleavage of the cyst from the rectum. The bladder, uterus, and vagina were retracted by stay sutures. The cyst was punctured and approximately 40 cc of purulent fluid was obtained, following intracystic injection of indocyanine green. This helped to meticulously dissociate the cyst from the surrounding muscular planes adjacent to the rectum, allowing it to extend caudally below the peritoneum into the pelvic floor. Complete excision of the cyst was macroscopically completed (see Video 1). Histological examination also revealed a morphology similar to that present in ACD, with columnar-squamous epithelial cells in the cranial end, a squamous epithelium in the caudal end, and smooth muscle cells in the wall. In addition to histological findings suggestive of ACD, the lesion’s extension beyond the pelvic floor further raised the suspicion of ACD. The postoperative course was uneventful, and she is in good health 1 year after surgery, with normal fecal continence.

Discussion

ACD is typically diagnosed early, in the first years of life, and there are few cases among older children [5]. Most commonly they remain asymptomatic, but clinical manifestations may become more apparent over time, often due to complications such as infection, mimicking recurrent abscesses or fistulae [3]. Diagnostic tools such as CT or MRI play a crucial role in evaluating retro-rectal masses, providing better insights into the tissue characteristics (ie, detecting calcifications in case of teratoma, or fluid-filled areas in case of lymphangioma), and their relationship with the surrounding structures (ie, the presence of spinal cord communication in cases of meningocele) [6,7].

Although the likelihood of malignancy remains low in case of ACD, surgical excision aiming for complete removal while preserving anorectal function is typically recommended for all patients, as early removal of the duplication can prevent potential future complications, including malignancy [8].

The choice of surgical approach depends on factors like anatomical localization, presence of an external orifice, surgical accessibility, and individual preferences. Various techniques, including trans-anal, trans-coccygeal, abdominal, and posterior sagittal approaches, have been described [9]. In the presented cases, the MCS-PS approach was chosen when an external orifice was present to preserve anorectal function. Due to the presence of inflammatory tissue during the dissection, a protecting stoma was created to safeguard the vitality of tissue regeneration and to mitigate the likelihood of fistula formation.

In the second case, due to the cyst being located exclusively within the ischiorectal fossa, after a multidisciplinary discussion, a robotic approach was preferred. To the best of our knowledge, it is the first case of ACD treated with a robot. The use of robotic assistance played a crucial role in facilitating a minimally invasive procedure, particularly within the confined space of the pelvis. The inherent magnification of the robotic camera and the dexterity of robotic arms played a crucial role in the precise mass excision within the confined areas [10,11]. Despite the rarity of cystic anal duplications, early surgical planning based on their location is paramount for determining the optimal surgical approach. This type of planning highlights the importance of a multidisciplinary approach and thorough preoperative assessment to achieve favorable outcomes in such cases.

Conclusions

Anal canal duplication should be considered in the differential diagnosis for patients presenting with lesions in the ischiorectal fossa. Clinical examination and radiological findings are essential for guiding the choice of surgical approach. For cases with an external orifice extending below the peritoneal reflection, a posterior approach may be suitable. Conversely, minimally invasive surgical techniques are preferable for those without an external opening. In this context, robot-assisted surgery offers notable advantages over standard laparoscopic approaches in the pelvic region.