The hypospadias penis has a glans which is ventrally open. A portion of the urethral tube is missing, and is replaced by a so-called urethral plate extending from the ectopic meatus to the glans gap, between the corpora cavernosa [2]. The condition is the result of a problem during the endodermal transformation into the urethra and its subsequent tubularization which, for some reason yet to be understood, is stopped before it is accomplished [2, 4].

Part of the tubular urethra below the hypospadic meatus is not surrounded by corpus spongiosum, but is directly covered by hypo plastic skin tightly adherent to the tubular urethra [5, 6]. The frenular artery is consistently missing. The dorsal aspect of the penis, except for the redundant dorsal prepuce, is normal.

The division of the corpus spongiosum is always proximal to the ectopic meatus. All distal tissues to this division of the corpus spongiosum are hypoplastic. All tissues proximal to this division of the corpus spongiosum are normal (Fig. 24.1).

Until now there’s no consensus on how to determine the severity of a hypospadias. Multiple classification methods have been suggested [6–8].

Some authors have proposed to classify the severity of the hypospadias according to the place where the division of the corpus spongiosum is located, rather than based on the location or the ectopic meatus [4, 5, 7–9].

Another frequently used classification is defining hypospadias according to the position of its meatus before dissection: distal hypospadias, mid-penile hypospadias, and proximal hypospadias (Fig. 24.3) [7].

This classification, as many published classifications, is mainly based on the position of the ectopic meatus, and is determined before deglovement [2, 7]. It is however considered to be an inaccurate criterion to define the severity of the hypospadias [7, 10]. The level of division of the corpus spongiosum is indeed a far more accurate criterion as it shows where the genital tubercle arrested its development [5, 6, 10]. This however can only be determined intra-operatively [6, 11].

This intra-operative classification, despite being more accurate, is not widespread used. Most of the studies published about hypospadias surgery use indeed the position of the ectopic meatus as a reference [7] (Figs. 24.4 and 24.5).

Many variants in hypospadias can be observed, form the very obvious one peno-scrotal ones, to some very light fors, where the meatus is orthotopic, but some of the typoc features are observed: an incompletely fused pretputium, some important chordee,…

Again, there is no consensus of all those milder forms of hypospadias should be considered as hypospadias, or better classified apart: do all the chordee without hypospadias present the same pathologic features as the classical hypospadias with important chordee, or even without? The debate remains open.

Hypospadias is recognized to be a multifactorial disorder, with genetic, endocrine and environmental influences.

The pathophysiology of hypospadias remains to be discovered. A recent study showed however that the microscopic organization of the smooth muscle fibers of the dartos tissue plays an important role in congenital penile malformation: the level of dartos disorganization appears strongly related to the severity of the clinical condition [12].

Several maternal–placental factors correlated with hypospadias have been identified. Risk factors associated with neonates small for gestational age such as prematurity, preeclampsia and placental insufficiency are found to be correlated with the incidence of hypospadias. Also there seems to be an association between the presence of maternal hypertension, prematurity and oligohydramnios in relation to the severity of hypospadias [13]. Preexisting maternal diabetes or mild gestational diabetes, epilepsy, renal failure, asthma, exposure to influenza during the first trimester are potential maternal risk factors for developing hypospadias [14–16]. An indirectly association with conception by medically assisted reproduction is observed [14]. The role of maternal age on the prevalence of hypospadias is under discussion.

Multiple genetic abnormalities have been identified as main etiologic factors in hypospadias. The foreskin of the hypospadias population has a manifest greater androgen receptor (AR) gene methylation [17].

An interaction between genetic, maternal and environmental factors is responsible for the development of hypospadias. The underlying etiologic cause leading to the specific hypospadias phenotypes is not fully discovered yet [18].