N-type anorectal malformations.

Three cases of N-type anorectal malformations have been encountered. Two girls with anorectal-vestibular fistulas (one with a normal anus and the other with mild stenosis) were typical of 15 other such cases in the literature. A boy with an anorectal-urethral fistula and covered anus had a lesser variant than most of the other 8 males in the literature. The frequently accompanying esophageal, renal, and skeletal anomalies were not present, nor did he have anterior urethral hypoplasia. The constellation of other major associated anomalies in the boys, but not in the girls, follows the pattern of other types of anorectal malformations and suggests an earlier and/or more severe teratogenic insult in the boys. Anterior perineal resection of the fistula is appropriate for girls with N-type fistulas and for those boys with normal anterior urethras. An additional urethroplasty is necessary for boys with anterior urethral hypoplasia. Our experience and that from the literature suggest that N-type anorectal malformations constitute a rare but real entity, akin to N-type tracheoesophageal fistulas. A plea is made that they be included in classifications of anorectal anomalies.