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An imperforate anus or anorectal malformations (ARMs) are birth defects in which the rectum is malformed. ARMs are a spectrum of different congenital anomalies in males and females, that varies from fairly minor lesions to complex anomalies. The cause of ARMs is unknown; the genetic basis of these anomalies is very complex because of their anatomical variability. In 8% of patients genetic factors are clearly associated with ARMs. Anorectal malformation in Currarino syndrome represents the only association for which the gene HLXB9 has been identified.〔 ==Features== There are several forms of imperforate anus and anorectal malformations. The new classification is in relation of the type of associated fistula.〔Pena A, Levitt MA. (2006) "Anorectal Malformations" in: Grosfeld et al. Ed. "Pediatric Surgery", Mosly〕 The classical Wingspread classification was in low and high anomalies: * A low lesion, in which the colon remains close to the skin. In this case, there may be a stenosis (narrowing) of the anus, or the anus may be missing altogether, with the rectum ending in a blind pouch. * A high lesion, in which the colon is higher up in the pelvis and there is a fistula connecting the rectum and the bladder, urethra or the vagina. * A persistent cloaca (from the term cloaca, an analogous orifice in reptiles and amphibians), in which the rectum, vagina and urinary tract are joined into a single channel. Imperforate anus is usually present along with other birth defects—spinal problems, heart problems, tracheoesophageal fistula, esophageal atresia, renal anomalies, and limb anomalies are among the possibilities.〔Colorectal Center, Cincinnati Children's Hospital Medical Center. "(Anorectal Malformations / Imperforate Anus )." Retrieved July, 2005.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「imperforate anus」の詳細全文を読む スポンサード リンク
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