Anorectal Malformations

What are Anorectal Malformations?

Anorectal malformations are a group of birth defects than involve the external opening of the anus preventing the normal passage of stool. The anal opening may be smaller than normal size; in an abnormal location or not visible upon examination.

There are many types of anorectal malformations. Some of the more common types include:

Anal Stenosis/Atresia – a narrowing or complete absence (closure) of the anal opening.

Anoperineal/Rectoperineal fistula – a small tube-like opening that creates an abnormal passageway between the colon and the anal opening.

Ectopic Anus – an anal opening that is not in the normal place.

Perineal anus – an anal opening within the perineum.

Imperforate anus – the anal opening is completely closed or narrowed to only a small passage. A complete imperforate anus is often associated with atresia of the lower rectum.

“high type” – the rectum ends above pelvic nerve and muscle structures.

“low type” – the rectum extends completely or partially through the pelvic nerve and muscle structures.


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