Hypospadias is the term used to describe the abnormal anatomic location of the urethral meatus on the ventral aspect of the penis. Rarely, the urethral meatus is formed on the dorsal surface of the penis (epispadias). The incidence of hypospadias is approximately 8.2 in every 1000 male births.

The embryologic origin of the penis is a midline mesodermal mass called the genital tubercle, which appears at approximately the fifth week of fetal life. Elongation of the genital tubercle into the phallus is under the influence of androgens secreted by the fetal testes. Parallel urogenital folds form on the undersurface of the developing penis, with the urethral groove lying between them. By the 14th week of gestation, the urethral folds unite over the urethral groove, completing formation of the penile urethra. Development of the external genitalia is completed by the 12th week of gestation (see Chap. 90).

The formation of the ventral foreskin of the penis is related to normal urethral development; failure of the urethra to reach the tip of the glans penis is accompanied by absence of the ventral foreskin. The absence of this portion of the foreskin causes an abnormal ventral curvature of the penis known as chordee. Hypospadias is frequently accompanied by chordee.

If normal development of the urethra is arrested and the urethral folds fail to fuse, the meatus may be found anywhere along the course of the penis from the perineum to the glans. Hypospadias is best classified according to the anatomic site of the meatus, such as glanular; coronal; distal, mid, and proximal shaft; penoscrotal; scrotal; and perineal (Fig. 93-3 and Fig. 93-4).