Hypospadias refers to a birth defect of the urethra in the male where the urinary opening is not at the correct location on the head of the penis. It is the second most common birth abnormality in boys, affecting approximately 1 of every 250. In approximately 90% of cases, the opening (meatus) is on or near the head of the penis (glans), referred to as distal hypospadias, while the remainder have proximal hypospadias with a meatus near or within the scrotum. Shiny tissue seen extending from the meatus to the tip of the glans, which should have made the urinary channel, is referred to as the urethral plate.
In most cases the foreskin is also underdeveloped and does not wrap completely around the penis, leaving the underside of the glans penis uncovered. There may also be downward bending of the penis, commonly referred to as chordee. This is found in 10% of distal hypospadias and 50% of proximal hypospadias at the time of surgery. The scrotum may be higher than usual to either side of the penis, called penoscrotal transposition, adding to the abnormal overall appearance.
Hypospadias is thought to result from failure of the urinary channel to completely tubularize to the end of the penis. The cause of hypospadias is not known. Most often, it is the only abnormal finding, although in about 10% of cases hypospadias may be part of a syndrome with multiple abnormalities.
The most common associated defect is an undescended testicle, which has been reported in approximately 3% of infants with distal hypospadias and 10% of those having proximal hypospadias. The combination of hypospadias and an undescended testicle sometimes indicates a disorder of sexual differentiation, and so additional testing may be recommended.