Urorectal septum malformation sequence. Report of six cases and embryological analysis.

We encountered six female infants with a specific pattern of developmental abnormalities of the urogenital and lower intestinal tracts. The anomalies included ambiguous genitalia, lack of perineal openings, and müllerian and urinary tract anomalies. Each patient had normal female chromosomes and normal adrenal gland function. We believe that this combination of anomalies represents a recognizable and specific sequence that is due to a failure of migration to and/or fusion of the urorectal septum with the cloacal membrane. This, in turn, we postulate, leads to persistence of the cloaca and cloacal membrane and failure of normal differentiation of the external genitalia. Persistence of the cloacal membrane results in absence of the urethral and vaginal openings and an imperforate anus. We propose calling this entity the urorectal septum malformation sequence.