Anorectal malformations
Malformações anorretais
CategoryDefinition
Anorectal malformations (ARMs) are birth defects (due to alterations in embryo development of hindgut or proctodeum) where the anus and rectum (the lower end of the digestive tract) do not develop properly. They occur in approximately 1 in 5000 live births. These comprise a wide spectrum of diseases, which can affect boys and girls, and involve the distal anus and rectum as well as the urinary and genital tracts. Several abnormalities can occur, including the following: A membrane may be present over the anal opening; The rectum may not connect to the anus (imperforate anus); The rectum may connect to a part of the urinary tract or the reproductive system through an abnormal passage called a fistula. The classification of ARMs is mainly based on the position of the rectal pouch relative to the puborectal sling, the presence or absence of fistulas, and the types and locations of the fistulas. The following classification is according to the level of the atretic rectal cul-de-sac with respect to the pubococcygeal line (the radiological landmark for the upper border or the levator ani muscle).