Anorectal atresia: prenatal sonographic diagnosis.

To determine the prenatal sonographic findings of anorectal atresia (ARA), we retrospectively reviewed 12 proven cases. Sonography showed abnormally dilated bowel segments in five cases (42%), four of which were identified prospectively; at autopsy, two other cases showed mild colon dilatation not evident on sonograms. Bowel dilatation was not associated with the location of atresia or the presence of a fistula, but was possibly related to menstrual age. Eleven fetuses (92%) had significant other anomalies primarily related to the VACTERL syndrome (vertebral defects, anal atresia, tracheoesophageal fistula with esophageal atresia, radial and renal dysplasia, and limb malformations) and/or the caudal regression syndrome; of these, sonography identified one or more concurrent anomalies in seven cases. In two cases, bowel dilatation was the primary sonographic finding. Death in nine cases resulted from termination of pregnancy (four cases) or perinatal demise (five cases); three patients are still alive. We conclude that some cases of ARA can be suspected on prenatal sonograms by demonstration of dilated colon, and that the sensitivity of this finding may be related to menstrual age at the time of the examination. Distinguishing ARA from other causes of fetal-bowel dilatation is important because of the frequency of concurrent anomalies associated with ARA.