Anorectal malformations and Down's syndrome.

BACKGROUND/PURPOSE: Down's syndrome is a common association in patients with anorectal malformations. The purpose of this study was to determine whether the anorectal defect in patients with Down's syndrome had specific characteristics and whether the presence of Down's syndrome represented a serious detriment to the patient's functional prognosis.

METHODS: Nine hundred eighty-seven patients with anorectal malformations were studied retrospectively. Twenty patients (2%) had Down's syndrome. Nineteen of these (95%) had the same specific type of anorectal defect: imperforate anus with no fistula. This defect has a good prognosis, the rectum is located about 2 cm above the perineal skin, the sacrum is normal, and the sphincter mechanism is good. For comparison, a group of 34 patients with the same defect but without Down's syndrome was also studied. All patients were operated on via posterior sagittal approach by the same surgeon.

RESULTS: Imperforate anus without fistula occurs in 5% of all patients with anorectal malformations and in 95% of those patients who also suffer from Down's syndrome. The characteristics of the defect were the same in both groups of patients, and surprisingly, the prognosis was good in both groups (80% to 96% of patients had voluntary bowel movement, 100% had urinary continence).

CONCLUSIONS: The association of Down's syndrome with imperforate anus without fistula is not coincidental. This particular benign defect can be predicted to occur in most patients with Down's syndrome. The presence of Down's syndrome in cases of anorectal malformations should not be a contraindication to repairing the imperforate anus and to closing the colostomy.