Hypospadias

Hypospadias is a male birth defect in which the opening of the urethra develops abnormally, usually on the underside of the penis, anywhere from below the tip of the glans toward the scrotum. Instead of opening at the tip of the glans, a hypospadic urethra opens along the urethral groove on the ventral aspect of the shaft, from the glans down to the penoscrotal junction or perineum.

Hypospadias is among the most common birth defects of the male genitalia (second only to cryptorchidism), with widely varying reported incidence. The incidence of hypospadias has increased in recent decades in some populations. In the United States, surveillance studies described a rise from about 1 in 500 total births (1 in 250 boys) in the 1970s to 1 in 250 total births (1 in 125 boys) in the 1990s. Globally, trends differ by region and registry; some studies report increases, others stable or decreasing rates.

A distal hypospadias may be suspected even in an uncircumcised boy because of an abnormally formed foreskin and downward tilt of the glans.

The urethral meatus opens on the underside of the glans or on the penile shaft in roughly 50-75% of cases; these are grouped as distal forms. Proximal forms (meatus from the penoscrotal angle toward the perineum) occur in up to about 20-30% of cases. More severe degrees are more often associated with chordee (ventral curvature due to tethering of the phallus) or undescended testes (cryptorchidism).

Mild hypospadias is often an isolated finding without other reproductive or endocrine anomalies. A minority of infants, especially with more severe hypospadias, have additional genitourinary structural anomalies. Up to about 10% of boys with hypospadias have at least one undescended testis, and a similar proportion may have an inguinal hernia. An enlarged prostatic utricle is more common when hypospadias is severe (scrotal or perineal) and can predispose to urinary tract infections, voiding symptoms, or stone formation.

In most cases the cause is not fully understood. Maternal exposure to hormones such as progesterone during pregnancy may increase risk. Certain hormonal milieus in fetal life - for example inadequate fetal testosterone production or impaired response to androgen - increase the risk of hypospadias and related genital differences. Sometimes hypospadias is familial.

Some data suggest higher risk in male infants from late pregnancy or after in vitro fertilization (IVF), possibly related to progesterone or progestin exposure during treatment.

Prenatal testosterone, converted in genital skin to dihydrotestosterone, supports migration of fibroblasts to enclose the urethral groove; failure of adequate prenatal androgen effect is thought to contribute to many cases, so severe hypospadias is sometimes discussed as a mild form of under-virilization in a genetic male. Postnatal androgen deficiency is demonstrable only in a minority; transient fetal deficiency during critical windows has been proposed, including interactions with anti-Müllerian hormone and pituitary-gonadal function. Transcription factor abnormalities have also been implicated.

In a subset of patients, postnatal androgen deficiency or reduced androgen sensitivity is documented, often with chordee; in severe cases a residual perineal urogenital opening and small phallus may occur - sometimes termed pseudovaginal perineoscrotal hypospadias within the spectrum of ambiguous genitalia. Postnatal testosterone does not “close” the urethra by itself. Genetic factors likely contribute; familial recurrence risk is on the order of about 7%. Research has reported higher risk in association with specific X-linked genetic variants.

Distal forms (glanular, subglanular, midshaft) are often repaired between 12 and 18 months of age. More than 200 operative techniques and modifications exist; overall success rates are often quoted in the 90-95% range for distal repairs. Single-stage repair is common when anatomy is favorable, typically by a pediatric urologist or experienced reconstructive surgeon, frequently before one year of age in planned elective schedules.

When hypospadias is severe or there are associated findings such as chordee or cryptorchidism, management may be staged. A karyotype and endocrine evaluation may be indicated to exclude intersex conditions or hormone deficiencies. If the penis is small, testosterone or hCG may be used preoperatively to improve tissue bulk. Severe repairs may require multiple stages and mucosal grafting; preputial skin is often valuable for grafting, so circumcision should be avoided before definitive repair when foreskin may be needed.

Operative steps are individualized; they typically include urethral plate work, correction of chordee as needed, and reconstruction of the glans and skin coverage (urethroplasty and glansplasty) according to the chosen technique.

In a minority of patients with severe hypospadias, outcomes may include scarring, recurrent curvature, or urethral problems such as fistula (an extra opening along the repair line), diverticulum (outpouching of the urethral lining affecting stream or causing post-void dribbling), or stricture (narrowing that obstructs flow). In high-volume centers, even complex repairs report improved complication profiles over time. A particular challenge is urethral complications in adulthood after childhood repair; in these situations, principles of adult urethral reconstruction apply for successful secondary repair.