Genetics, Pathogenesis and Epidemiology of Anorectal Malformations and Caudal Regression Syndrome

Abstract

Anorectal malformations (ARM) represent a complex group of congenital anomalies resulting from abnormal development of the hindgut, allantois and Mullerian duct, leading to incomplete or partial urorectal septal malformations. ARM are a relatively uncommon congenital cause of intestinal obstruction in the newborn, occurring in approximately 1 out of every 4,000–5,000 births (4.05 per 10,000 births). Approximately 36.4% are isolated lesions and 63.6% are associated with other anomalies. Chromosomal defects are associated in 8% and a family history may be present. There are epidemiological differences in the level and extent of the abnormality. In the landmark study of 2,376 patients by Stephens, 45% were “rectal” and 53% “anal”.Although the current understanding of normal development and pathologic variations of ARM is incomplete, the critical period of organogenesis is understood to be at or before the 6–7^th week of gestation. As a result, any aetiological defect would have to occur very early on in development.