Internal and external genitalia

Figure 33-1. Summary of sexual differentiation impact of genetic sex on differentiation of the bipotential gonad and role of the hormonal milieu on development of the primor-dia of the internal duct system and external genitalia in utero.

Patients normally present in the neonatal period or in infancy and there is a male-to-female ratio of 1 2. The patient may present with constipation, with obstruction if the cyst is of large size, or may present with bleeding if the cyst communicates with the normal gut lumen, and if there is ulceration of gastric mucosa within the duplication cyst. Duplication cysts may be associated with recto-genital or recto-urinary fistula, duplication of the internal or external genitalia, vertebral anomalies and multi-system congenital anomaly complexes. Female patients... 

Definitive evidence that dihydrotestosterone (DHT) is a potent androgen with its own important physiological and pathophysiological actions, separate from those of testosterone, was provided by two reports in 1974 of a rare inborn disorder of male phenotypic sexual differentiation caused by a deficiency in 5a-reductase, the enzyme that converts testosterone to DHT. The reduction in the conversion of testosterone to DHT by 5a-reductase, which underlies this syndrome, leads to a specific developmental defect in the formation of the male external genitalia and the prostate. Males with this genetic disorder exhibit a striking phenotype, in which the internal genitalia are normal... 

Anatomic Considerations The internal pudendal artery, a terminal branch of the anterior division of the internal iliac artery supplies the external genitalia. With extension to inguinal and iliac lymph nodes, additional supply originates from the obturator branch of the internal iliac artery, the inferior epigastric artery from the external iliac artery and the superficial epigastric artery and the superficial and deep external pudendal branches of the common femoral arteries. 

There is very little in the published literature about specific genitourinary injuries, although clearly the external genitalia (in men) are at risk of burns and fragment injury and the internal genitalia are at risk of penetrating injury. 

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