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21. What are the urogenital sinus abnormalities seen in a 46,XX newborn with
    CAH due to 21α-hydroxylase defi ciency?

In the absence of androgens, the urogenital sinus differentiates into urethra and

lower one-third of the vagina during organogenesis; however, on exposure to

circulating androgens, the urogenital sinus differentiates into prostate and ure-

thra. In a female embryo, the urogenital sinus differentiates into urethra and

vagina with two distinct openings at the perineum. However, in a female

embryo with CAH, exposure to high levels of adrenal androgens during uro-

genital development (7–12 weeks of intrauterine life) prevents differentiation

of the urogenital sinus into the urethra and lower one-third of the vagina and

results in persistence of the urogenital sinus. This is clinically evident as single

common opening for urethra and Mullerian derivatives in a patient with

CAH. However, depending on the level and sensitivity to androgens, the site of

Mullerian duct opening into the urogenital sinus can be located near the peri-

neal surface (low vaginal confl uence) or away from it (high vaginal confl uence)

(Fig. 10.7 ).

22. Why is it important to differentiate between low- and high vaginal confl uence?

The differentiation between low- and high vaginal confl uence can be made by

performing either genitoscopy or urogenitogram. This is important in determin-

ing the nature and timing of genital reconstructive surgery. Children with low

Low Vaginal Confluence

High Vaginal Confluence

ac

b

c

Fig. 10.7 ( a , b ) Urogenital sinus with low vaginal confl uence and high vaginal confl uence. ( c )
Sinogram of a patient with ovotesticular DSD showing low vaginal confl uence ( red arrow )

10 Congenital Adrenal Hyperplasia