Anorectal atresia consists of absence of an anus ("imperforate anus") or a lack of passage through the rectum or from the rectum to the anal canal. It may be associated with a fistula to urethra, bladder or vagina. The anal opening may also be dislocated from its normal site. In the majority of affected infants, other malformations exist, often serious ones. An anorectal atresia repaired, although often a normal functional anus cannot be produced. The initial operation in the newborn is usually followed by supplementary repair at a later age.
In most parts of the world, the incidence of anorectal atresia is around 3 per 10,000 births; the rate in Japan is around twice as high. Most trends show a steady decrease in the rate of incidence.