Hypospadias

Description

Hypospadias occurs in about 1/300 male infants and is characterised by displacement of the urethral meatus ventrally and proximally from the tip of the glans penis. In first degree hypospadias the urethral meatus is in the distal third of the penis (glandular or coronal). In second degree the opening is between the distal third to the penoscrotal junction (penile) and in third degree the opening is scrotal or perineal. In approximately 50% there is chordee or downward curvature of the glans penis resulting in penile deformity. Epispadias occurs about 1/30,000 male infants and is characterised by a urethral meatus on the dorsal surface of the penis. It may occur as an isolated condition but is often associated with exstrophy of the bladder. In males the urethral groove begins to fuse in the pelvic region at about 8 weeks gestation with the urogenital ostium progressing to the phallus by 14 weeks. The glans is the last portion to close. Failure of fusion (or hypospadias) is the result of inadequate production of androgens by the fetal testes and/or inadequate receptor sites. Differences in timing, the degree of hormonal failure or failure of development of receptor sites account for the different types of hypospadias. With scrotal and perineal hypospadias the labioscrotal folds fail to fuse and the urethral orifice is located between or below the unfused halves of the scrotum. In epispadias the genital tubercle is thought to develop more dorsally than normal so that when the urogenital membrane ruptures, the urogenital sinus opens on the dorsal surface of the penis and urine is expelled at the root of the malformed penis. Most cases of hypospadias are multifactorial with approximately a 9-10% recurrence risk. Maternal progestin exposure during the vulnerable period may increase the incidence of hypospadias in predisposed fetuses. Single gene inheritance (AD or AR) is possible in a small number of families with isolated hypospadias. Androgen receptor defects have also been described in some cases. Associated defects occur in about 8-9% of cases (primarily genital or inguinal). Chromosomal abnormalities were reported by Aarskog in 7.5% of cases.