Urogenital Sinus
A.  Vagina
B.  Urethra
C.  Confluence of vagina and urethra
D.  Urogenital sinus
B
A
C
D
A variety of conditions may result in abnormal sexual differentiation in the developing fetus. These include excessive androgen in females, deficient synthesis or metabolism of testosterone or end organ insensitivity in males, and abnormalities of the sex chromosomes or gonads themselves. Anomalous or ambiguous genitalia in the newborn are important socially. Paramount in the decision on how to rear a child as male or female is the identification of the uterus, vagina or urogenital sinus (UGS) by ultrasound, fistulogram or vaginogram. A urogenital sinus anomaly should be suspected whenever there is a single perineal opening and any ambiguity of the external genitalia. A detailed radiographic study of the lower genitourinary tract is important for diagnosis. In patients with a UGS, there is a common terminal channel for the anterior urethra and posterior vaginal pouch. The sinus empties at the base of the phallus. The UGS can vary in appearance, being quite short and joining the vagina close to the perineal surface, or very long, joining the vagina near the bladder neck. The length of the UGS and level of insertion of the vagina are good indicators of the degree of virilization that has taken place. The presence of a cervical imprint in the vagina is also extremely important, being present in all female intersex patients. A voiding cystourethrogram (VCUG) in the lateral view may be all that is necessary for anatomic evaluation. Separate catheterization of both the bladder and vagina may be performed, or retrograde injection of the common channel may be necessary to delineate the anatomy. A coude-tipped catheter may be beneficial to manipulate placement under fluoroscopy into the desired position. Adequate distention of the vagina is important if one is to accurately assess for the presence of a cervical impression. Pelvic ultrasound is the best tool for identification of uterine tissue. Ovaries are often seen and adrenal tissue can be assessed. Magnetic resonance imaging (MRI) is reserved for complex anatomy. References: Caffey's Pediatric Diagnostic Imaging. Tenth Edition. 2004, Elsevier Inc. pp 1967-1978