anorectal anomalies anorectal anomalies anorectal anomalies are congenital malformations of the anus and rectum. one anal anomaly, imperforate anus has an estimated incidence of 1 in 5000 births. it affects boys and girls with similar frequency. not to be confused with anorexia. examples of anorectal anomalies include: anal stenosis proctitis anal bleeding anal fistula