Imperforate anus
- 1/4000
- a spectrum of defects
- three anatomic groups based on the relation between the rectum and the
levator ani muscle
- the levator ani muscle comprises the anterior two thirds of the floor of
the pelvis, through which the rectum, vagina, and urethra pass through. (the
posterior 1/3 is covered by the ischo-coccygeus muscle and piriformis muscle)
- low, intermediate and high refer to how far down the rectum goes, using
the external skin as a 'floor' reference, low being closer to the
surface (and therefore better), high being farther from the skin.
Low imperforate anus
- rectum passes through the levator ani completely and ends as a small
opening in the anal region in the center of a prominent ridge, “bucket handle”
deformity (a bridge of tissue divides the anus into two holes), good prognosis for continence
- no colostomy required
Intermediate Lesions
- are partially translevator
- requires colostomy and later a pull through procedure
- usually have a good outcome and potential for continence
High Lesions
- fail to pass through the levator ani, no visible external fistula,
usually the rectum ends as a fistula into the prostatic urethra in boys or
into the vagina in girls;
- usually assoc with GU and lumbosacral abnormalities
- repair requires colostomy and later a pull through procedure
CHLA Board Review 2005