LAUSR

Anal canal duplication (ACD) is the rarest among the duplications of the alimentary tract and can be defined as a duplication along the posterior side of the anal canal, with a perineal orifice situated just behind the anus. It is often found on simple perineal inspection as sagittally located double anal orifices with no symptoms. Other diseases such as fistula in ano, hindgut or rectal duplications need to be differentiated from ACD anatomically or on pathology. This report describes the rare case of a 14-year-old girl with ACD and perineal abscess. We discuss the characteristics of this type of disorder, particularly symptoms associated with ACD. A 14-year-old girl with no significant medical history presented with fever and perianal pain. The fact that she had two holes in the anus had been noted by her family since the age of 1, but this was ignored. She had not complained of constipation or anal pain. On perineal inspection, redness, swelling and induration were seen around a perianal orifice located in the midline posterior to the true anus. Enhanced computed tomography showed marked fluid collection in the back of the rectum surrounded by a thick wall that was partially contrasted, measuring 5.4 9 3.5 9 4.0 cm in diameter (Fig. S1). I.v. antibiotics were started immediately and the patient recovered without surgical drainage. The patient was referred to Hokkaido University Hospital for further evaluation and treatment to prevent recurrent abscess formation. On physical examination, the anus was normally located, and no anorectal stenosis was observed. Perianal orifice was evident without redness or fluid discharge (Fig. 1). There was no perineal pain on palpation. Fistulography showed a 3-cmlong narrow canal without connection to the rectum. Pelvic magnetic resonance imaging clearly showed normal muscle components, but the anatomical relationship between the ACD and the surrounding muscle structures were not obvious. On colorectal endoscopy, a fistula opening was not found at the rectal wall. The patient underwent surgical removal of the ACD by a perineal approach. The lesion circumscribing the orifice was removed with incision, and the fistulous tract dissected carefully from the external anal sphincter and part of the striated muscle complex, which were detected with an electric stimulator. Although the wall at the cranial end was partly shared with the rectum, it was resected completely without rectal injury. The removed ACD had a narrow fistula, measured approximately 30 mm in diameter, and had no connection to the rectum. Histopathology showed stratified squamous epithelium and partially columnar epithelial lining, with a small amount of adjacent smooth muscle bundles (Fig. S2). Pathology confirmed a final diagnosis of ACD. The postoperative clinical course was uneventful and the patient has had good bowel function with normal appearance of the perineum for 1 year after the operation. Abscess formation associated with ACD is extremely rare: only five cases in children have been previously reported in the literature. Of the six total patients, including the present one, all were female and the average age of presentation was 64 months (range, 0–14 years). All patients except one had duplications that were tubular in structure. Internal communication with the native anal canal was present in two patients. Although one patient had additional anomalies (tethered cord Fig. 1 Small anal canal duplication orifice visible in the midline (arrow) posterior to the normally located anus.