Genetics, Pathogenesis and Epidemiology of Anorectal Malformations and Caudal Regression Syndrome
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 6–7th week of gestation. As a result, any aetiological defect would have to occur very early on in development.
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