Hypospadias is an abnormality of anterior urethral and penile development in which the urethral opening is ectopically located on the ventral aspect of the penis proximal to the tip of the glans penis, which, in this condition, is splayed open. The urethral opening may be located as far down as in the scrotum or perineum. The penis is more likely to have associated ventral shortening and curvature, called chordee, with more proximal urethral defects.
The earliest medical text describing hypospadias dates back to the second century CE and was the work of Galen, the first to use the term. During the first millennium, the primary treatment for hypospadias was amputation of the penis distal to the meatus. Since that time, many have contributed to development of modern hypospadias repair. More than 300 different types of repairs have been described in the medical literature. Although most reports have been in the past 60 years, most basic techniques were described over a century ago.
Modern anesthetic techniques, fine instrumentation, sutures, dressing materials, and antibiotics have improved clinical outcomes and have, in most cases, allowed surgical treatment with a single-stage repair within the first year of life on an outpatient basis.
Hypospadias is a congenital defect that is thought to occur embryologically during urethral development, between 8 and 20 weeks' gestation. The external genital structures are identical in males and females until 8 weeks' gestation; the genitals develop a masculine phenotype in males primarily under the influence of testosterone. As the phallus grows, the open urethral groove extends from its base to the level of the corona.
The classic theory is that the urethral folds coalesce in the midline from base to tip, forming a tubularized penile urethra and median scrotal raphe. This accounts for the posterior and middle urethra. The anterior or glanular urethra is thought to develop in a proximal direction, with an ectodermal core forming at the tip of the glans penis, which canalizes to join with the more proximal urethra at the level of the corona. The higher incidence of subcoronal hypospadias supports the vulnerable final step in this theory of development.
In 2000, Baskin proposed a modification of this theory in which the urethral folds fuse to form a seam of epithelium, which is then transformed into mesenchyme and subsequently canalizes by apoptosis or programmed cell resorption.  Similarly, this seam theoretically also develops at the glanular level, and the endoderm differentiates to ectoderm with subsequent canalization by apoptosis.
The prepuce normally forms as a ridge of skin from the corona that grows circumferentially, fusing with the glans. Failure of fusion of the urethral folds in hypospadias impedes this process, and a dorsal hooded prepuce results. On rare occasions, a glanular cleft with intact prepuce may occur, which is termed the megameatus intact prepuce (MIP) variant.
Chordee (ventral curvature of the penis) is often associated with hypospadias, especially more severe forms. This is thought to result from a growth disparity between the normal dorsal tissue of the corporal bodies and the attenuated ventral urethra and associated tissues. Rarely, the abortive spongiosal tissue and fascia distal to the urethral meatus forms a tethering fibrous band that contributes to the chordee. (See the image below.)
The location of the abnormal urethral meatus classifies the hypospadias. Although several different classifications have been described, most physicians use the one proposed by Barcat and modified by Duckett, which describes the location of the meatus after correction of any associated chordee. [2, 3] Descriptive locations described include the following:
Anterior (glanular and subcoronal)
Middle (distal penile, midshaft, and proximal penile)
Posterior (penoscrotal, scrotal, and perineal)
The location is anterior in 50% of cases, middle in 20%, and posterior in 30%; the subcoronal position is the most common overall. (See the images below.)
Hypospadias occurs in approximately 1 in every 250 male births in the United States. The incidence doubled from 1970 to 1993. Although some have suggested that this doubling actually reflects increased reporting of minor grades of hypospadias, increases in severe hypospadias have also been noted. Increasing sensitivity of surveillance systems alone cannot explain this twofold increase. However, some reports have linked the increased rate of hypospadias in boys born prematurely and small for gestational age and boys with low birth weight.
In several countries, the incidence of hypospadias may be rising. In general, the frequency seems rather constant, at 0.26 per 1000 live births in Mexico and Scandinavia and 2.11 per 1000 live births in Hungary. 
The treatment for hypospadias is surgical repair. Hypospadias is generally repaired for functional and cosmetic reasons. The more proximally ectopic the position of the urethral meatus, the more likely the urinary stream is to be deflected downward, which may necessitate urination in a seated position. Any element of chordee can exacerbate this abnormality. Fertility may be affected. The abnormal deflection of ejaculate may preclude effective insemination, and significant chordee can preclude vaginal insertion of the penis or can be associated with inherently painful erections.
Although the most minor forms of hypospadias are insignificant in physiologic terms, they too may merit repair on the basis of the potential psychological stress associated with having a genital anomaly.
The incidence of hypospadias is higher in whites than in blacks, and the condition is more common in those of Jewish and Italian descent. A genetic component may be present in certain families; the familial rate of hypospadias is about 7%.