Anal canal duplication in childhood.

Anal canal duplication is an extremely rare abnormality. Two cases in children are reported; in both cases, the orifice of the duplicate tubular structure was located just behind the normal anus and ran along the posterior side of the anal canal without communication with the anorectum. Complete removal of the duplication was performed through a perineal approach. Histology revealed a squamous lining with a smooth-muscle component around the cavity, with mucus-secreting transitional epithelium. Anal ducts with apocrine secretion and lymphocyte infiltration were also observed. The postoperative clinical courses were uneventful with satisfactory anal function. We collected nine similar cases from the literature. The term "anal canal duplication" is proposed based on common clinical features and pathology.