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Findings:
Direct catheterization of the bladder with filling of the urethra and reflux of contrast into an elongated vagina and rectum (subsequent uterus and colon) through a common cloacal opening.

Diagnosis: Persistent cloaca

Discussion: Normally the cloaca is divided by a coronal sheet of mesenchyme called the 'urorectal septum' which grows caudally toward the clocacal membrane. This septum produces lateral extensions which grow toward each other and fuse, dividing the cloaca into the rectum and upper anal canal dorsally and the urogenital sinus ventrally.

The urorectal septum fuses with cloacal membrane by the end of the sixth gestational week forming a fibromuscular node called the "central perineal tendon" or 'perineal body' which is a landmark for the converging muscles that insert into it. The urorectal septum divides the cloacal membrane into a dorsal "anal membrane" and a larger central urogenital membrane. It also divides the cloacal sphincter into anterior muscles (including the urogenital diaphragm), and the posterior external anal sphincter. The anal membrane usually ruptures at the end of the eighth week, creating the anal canal.

Failure of the urogenital and urorectal septa to separate the rectum, vagina, and urethra results in persistence of the primitive fetal cloaca. The distal end of the vagina may be stenosed, causing hydrometrocolpos. The uterus may be duplicate or bicornuate. The sacrum is frequently deformed. Coexisting anomalies may be present in any system.

Imperforate anus on physical exam with a single opening behind the clitoris in a newborn female with normal or ambiguous genitalia should raise suspicion for this entity. VCUG is performed to outline the anatomy if catheterization of the bladder is possible. If not, a vaginogram or retrograde injection through the cloaca may confirm the diagnosis.

References:
1. Caffey's Pediatric x-ray Diagnosis. ED. Silverman FN; Kuhn JP © 1993.
Mosby, St. Louis, Mo. pp-1389-90.

2. The Developing Human Keith L. Alcore, Ph.D. © W.B. Saunders Co.,
Philadelphia pp-248-249.

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