Anal canal duplication (ACD) is a very rare condition, diagnosed and treated mostly in childhood. Less than 90 cases have been reported in the literature so far. We are presenting a case of a young woman who underwent surgical excision of the duplication when she was 27 years old. The patient was unaware of her condition and was referred from a gynaecological office to the surgical department with a history of perianal discomfort and mucus discharge. Local examination showed an external orifice posterior to the anal opening, on the median line, which had the macroscopic appearance of a secondary anal orifice. The opening was about 0.5 cm in diameter. Exploration of the tract revealed a length of about 4 cm. MRI described the aforementioned tract, parallel to the anal canal, with no other anomalies mentioned. Under spinal anesthesia, with the patient in jackknife position, the accessory anal canal was surgically excised. The pathology report showed the presence of smooth muscle fibers and typical anal glands in the specimen. After a five-year follow-up, the patient showed no recurrence or any other related local symptoms. Absence of perianal abscess from the patient history, along with the macroscopic aspect of the opening similar to a secondary anal orifice on the midline, should raise the suspicion of ACD. Due to the lack of bothersome symptomatology, the patient did not seek any special investigations for her condition until she was in her late twenties. ACD is a very rare condition in adults that might pass unnoticed, but a midline opening posterior to the anus should always raise the suspicion of a secondary anal canal. Surgery is the only cure for this condition with good results after a proper pre-operative workout to reveal others simultaneous malformations.
Keywords: adult anal duplication; anal canal duplication; ano-rectal malformations.