How accurate is prenatal sonography for the diagnosis of imperforate anus and Hirschsprung's disease?

Abstract

Imperforate anus (IA) and Hirschsprung's disease (HD) are the commonest causes of coloanal obstruction in the neonate. We prospectively studied 15,092 pregnancies over a 4-year period to determine the accuracy of prenatal sonography (US) in diagnosing these conditions. Based on location and appearance, 13 fetuses were thought to have colonic dilatation on prenatal US. Nine of these had dilated bowel located in the pelvis. Postnatally, 7 were normal and 2 had an IA. Four fetuses were thought to have dilated proximal colon based on the peripheral location of the bowel loops in the abdomen. All 4 had normal colons, but had small-bowel obstruction postnatally (3 meconium ileus, 1 malrotation). Neonatal or fetal pathologic follow-up was obtained for all pregnancies. Twenty-three fetuses without dilated colon on US had coloanal obstruction (20 IA, 3 HD). Other anomalies had been sonographically evident in 17 of these fetuses (all with IA).