EP06.29: Sonographic imaging of the fetal anus at early pregnancy: a prospective feasibility study

Sonographic imaging of the fetal anus is currently possible beyond 18 gestational weeks. The aims of this study was to assess the feasibility to image the fetal anus and ascertain normal anal canal anatomy, from 12 to 17 weeks of gestation. Normal anatomy was determined when the anal canal was continuous with the rectum, ending in the expected location on the fetal perineum. Low anal atresia was determined when a distended rectal pouch was continuous with an anteriorly deflected perineal fistula. High anal atresia was determined when a distended blind ending rectal pouch was demonstrated in the pelvis without a fistula to the fetal perineum. A total of 125 patients met the inclusion criteria, enrolled and scanned. The demonstration of the normal anal canal was feasible in all fetuses. Postnatal evaluation demonstrated normal anal canal anatomy for all the babies. During the study period, two fetuses suffering anal atresia were diagnosed at our Unit during the early second trimester, using the described scanning method. One with low anal atresia and one with high anal atresia. the integrity of the anal canal can be seen as early as 12 gestational weeks. This offers early diagnosis of anorectal malformations.