Although a female:male ratio of 2-3:1 is reported in the literature , all the four cases in the author's series were males. The presentation of a rectal duplication depends on the following factors: (1) the size and therefore the mass effect of the duplication, (2) the presence of a fistula, (3) infection in the duplication, (4) the presence of ectopic gastric mucosa with ulceration, and (5) malignant degeneration.
Rectal duplications are rarely symptomatic during the immediate neonatal period unless presenting as a rectal mass bulging outside the anal canal or a mucosal-lined fistulous tract opening in the midline posteriorly or, rarely, anteriorly [11-14]. Since the cyst expands slowly and is located in the retrorectal area, compression of the rectum and lower urinary tract may result. The lack of suspicion due to its rarity explains the diagnostic difficulties. The cystic rectal duplication can be palpated on rectal examination as a smooth, firm mass that bulges into the rectal lumen from the sacral hollow.
As the duplication cyst slowly fills with the fluid, it enlarges causing local symptoms such as tenderness, low back pain, suprapubic pain, intestinal obstruction, dysuria, dystocia, or sciatic pain. Drainage of mucus or pus from the anus or from a perianal fistula is a frequent presenting sign. Fistulae are reported to occur in approximately 20% of cystic rectal duplications and involve the perianal skin posterior to the anus or the distal canal in the midline . The fistula rate of 45% in one series was based on both clinical and pathological examination, suggesting that not all communications are clinically evident . A characteristic finding is a cone-shaped dimple in the midline just posterior or anterior to the anal verge. It may rarely present as a perforated ulcer . No case with communication to the urinary tract has been reported, although some patients presented with urinary tract symptoms due to compression by a large duplication. Many of these patients who were misdi-agnosed initially underwent drainage of an apparent perirectal abscess or marsupialization of a fistula-in-ano only to suffer multiple recurrences.
Patients may present with a nonspecific picture of gastroenteritis in a setting of failure to thrive and a past history of recurrent urinary tract infections. Malignant degeneration in rectal duplications has also been reported in the adult age group; usually adeno-carcinoma, rarely carcinoid [17,18].
The authors' experience with the management of four rectal duplication cysts is as follows:
Case 1. A 9-month-old-male child was found to have three duplication cysts in the midline posterior to the rectum, during a posterior sagittal anorectoplasty (PSARP) procedure. The cysts were very small (0.5-1.0 cm), tubular, looked like segments of intestine, and were attached loosely to each other longitudinally; however, they were not adherent to the rectum. The cysts were easily excised and the diagnosis established histopathology. Rectal duplication was not suspected preoperatively and it was only a chance finding during the surgery.
Case 2. A newborn male child presented with a defect in the perineum around the anus anteriorly. A tongue of the anal mucosa extended from the anal verge high up for about 3 cm. There was mucus discharge and the baby was incontinent. On examination, there was an incomplete tubular structure about 3 cm long situated in the midline just anterior to the anal verge. It was lined by mucosa that communicated freely with the rectum and the anal canal. The
Fig. 13.2 Computed tomography scan showing a fluid-filled retrorectal cyst suggestive of rectal duplication (photograph and case 5 details, courtesy of Dr. Shivkumar, Trivandrum, India)
r w cyst was excised from the perineum and the defect repaired. The anal sphincter was reconstructed and the postoperative result was good, with development of full continence.
Case 3. A 6-month-old male baby presented with constipation and a cystic mass bulging from the anal verge. A computed tomography (CT) scan confirmed the presence of a fluid-filled mass located posterior to the rectum. It extended up for 5 cm from the anal verge. Needle aspiration of the cyst revealed fluid mixed with mucus. The cyst was located posteriorly but extended laterally more on the left side. The cyst and the rectum shared a common muscular wall that could be separated carefully. It was excised via a posterior sagittal route. The rectal wall was repaired and the postoperative result was excellent.
Case 4. A 12-year-old boy presented with perineal hypospadias and ARM. A fistulous opening was present in the perineum between the neoanus and the hy-pospadiac meatus. A fistulogram delineated a 4-cm-long tract anterior to the rectum ending in a blind tubular structure. An anorectoplasty was done and the hypospadias was repaired, separating the urethra from the fistulous tract and the anus, under cover of a colostomy. Excision of the rectal duplication cyst has been deferred for fear of injury to the posterior urethra and the possible risk of fecal incontinence resulting from the surgical intervention. The patient is under regular follow-up with the complaint of only an occasional mild discharge from the fistula.
Case 5. An 18-month-old male baby presented with acute urinary retention and constipation from the previous 6 months. On examination, the bladder was palpable. Per rectal examination revealed a retro-rectal cystic mass. CT scan confirmed the findings of a retrorectal cystic mass (Fig. 13.2). Surgery via a posterior sagittal route revealed a common wall between the cyst and the rectum. The cyst could be separated carefully from the common muscular wall and was excised completely. The rectal wall was repaired. A covering colostomy was performed, which was closed after 2 months. A histopathological examination established the diagnosis.
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