Paediatrics: Anorectal malformations

Anorectal malformations

The incidence of anorectal malformation is 1/5000 live births. Anorectal malformations comprise part of the VACTERL association. The abnormality should be identified at birth. The baby presents with:

•   failure to pass meconium;

•   abdominal distension;

•   bile-stained vomiting.

Anatomy

The precise anatomy varies but the malformation can be subdivided into high and low/intermediate anomalies in males and females.

Low/intermediate anomalies

•   Rectum is present and passes through a normal sphincter complex.

•   In boys (Fig. 23.17) there is a tiny fistulous track to the surface of the perineum, often anteriorly on to the scrotum. If meconium is visible on the perineum a local ‘cut-back’ procedure can be performed to open the fistula back to the rectum in anticipation of normal continence.

•   In girls (Fig. 23.18) the rectum usually opens into the back of the introitus as a rectovestibular fistula. This abnormality is termed intermediate because, although normal continence is to be expected, reconstruction involves division of a common wall between rectum and vagina. For this reason treatment involves a 3-stage procedure with defunctioning colostomy, anorectal reconstruction, and then closure of the stoma.

•   Vesicoureteric reflux is very common.

High anomalies

•   These anomalies are rare in girls but common in boys (Fig. 23.17).

•   The sphincter complex is poorly developed and the prospects for continence are mediocre.

In boys the rectum makes a fistulous connection with the urethra. Treatment involves a defunctioning colostomy within the first 48hr of birth, reconstruction at a few months of age (most commonly involving a posterior sagittal anorectoplasty performed through a midline perineal incision), and then closure of the colostomy.