Descriptive epidemiology of isolated anal anomalies: a survey of 4.6 million births in Europe.

The prevalence of anal anomalies among 4,618,840 births recorded in 33 EUROCAT registries between 1980 and 1994 was 4.05 per 10,000 births. Of the 1,846 recorded cases, 672 (36.4%) were isolated anal anomalies while 1,174 (63.6%) occurred together with other anomalies. Only isolated anal anomalies were analyzed in this study: 75.5% were atresias, 10.1% of which were above and 89.9% were below the level of the levator ani muscle. Fistula occurred in 53% of supralevator and 37% of infralevator atresia. Other anal anomalies were ectopic anus (3.4%), congenital anal ®stula (14.7%), and persistent cloaca (0.9%). There was a predominance of males in anal atresia without ®stula (male to female (M:F) ratio was 6.7 for supralevator and 2.3 for infralevator atresia), but no signi®cant sex difference in atresias with ®stula. There was a predominance of females in ectopic anus and congenital anal ®stula (M:Fˆ0.11 and 0.36 respectively). High frequencies of fetal deaths were recorded in supralevator atresia without ®stula (8.3%) and in persistent cloaca (11.1%). Mean gestational length and mean birth weights were reduced for persistent cloaca but were within normal limits for other isolated anal anomalies. Odds ratios (ORs) for mothers above 35 years were increased for supralevator atresia without ®stula, supralevator atresia with ®stula, and congenital anal ®stula. ORs for mothers below 30 years were slightly increased for supralevator atresia without ®stula and decreased for persistent cloaca. There were marked differences in prevalence and distribution of anal anomalies among the EUROCAT registries. The results indicated that there are epidemiological differences among the various types of anal anomalies which might re¯ect different embryological origins.