What is the pathogenesis of proximal hypospadias?

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Objective: To report the information concerning the pathogenesis of proximal hypospadias and causes ofcurvature associated with it.Material and methods: From January 2009 to December 2015, 74 patients underwent repair of proximalhypospadias. In 70 patients we performed a systematic biopsies in the lateral areas of the urethral plate, aswell as under this plate. The study of the histological structure of these areas was performed using routinestaining with hematoxylin and eosin, and the Masson's trichrome which color the collagen fibers in blue andmonoclonal antibody against alpha-smooth muscle actin.Results: This prospective study shows that the fibrotic tissue abnormally present on the ventral side of thepenis 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, thesefibers may come from a blood vessel or spongy tissue which existed during neonatal period in the distal partof 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 fusionaround the urethra of two mesenchymal bodies. The arterial supply of this purely masculine formationoriginates from a new vascularization and it is probably, developed under secretion of androgens (angiogenicsubstances in target tissues).Conclusion: These findings allow us to suggest that the proximal hypospadias is due to avascular necrosisof the distal part ie. poorly vascularized part of the corpus spongiosum.