What is the pathogenesis of proximal hypospadias?

OBJECTIVE: To report the information concerning the pathogenesis of proximal hypospadias and causes of curvature associated with it.

MATERIAL AND METHODS: From January 2009 to December 2015, 74 patients underwent repair of proximal hypospadias. In 70 patients we performed a systematic biopsies in the lateral areas of the urethral plate, as well as under this plate. The study of the histological structure of these areas was performed using routine staining with hematoxylin and eosin, and the Masson's trichrome which color the collagen fibers in blue and monoclonal antibody against alpha-smooth muscle actin.

RESULTS: This prospective study shows that the fibrotic tissue abnormally present on the ventral side of the penis consists of a mixture of fibrous connective tissue, nerve nets, short vessels, and smooth muscle fibers. In contrast to the scrotal dartos, penile dartos fascia does not contain smooth muscle fibers. Therefore, these fibers may come from a blood vessel or spongy tissue which existed during neonatal period in the distal part of the penis before disappearing. In addition, in 13 cases, the presence downstream of the urethral meatus, of a bifurcation of corpus spongiosum into two branches supposes that the corpus spongiosum is form by fusion around the urethra of two mesenchymal bodies. The arterial supply of this purely masculine formation originates from a new vascularization and it is probably, developed under secretion of androgens (angiogenic substances in target tissues).

CONCLUSION: These findings allow us to suggest that the proximal hypospadias is due to avascular necrosis of the distal part ie. poorly vascularized part of the corpus spongiosum.