Anatomical studies of hypospadias.

PURPOSE

Hypospadias is the most common congenital anomaly affecting the penis. Successful repair depends on an accurate understanding of anatomy. We compared the anatomy of hypospadiac and normal fetal penises.

MATERIALS AND METHODS

A fetal penis at 33 weeks of gestation with distal shaft hypospadias was serially sectioned and compared to 10 normal human fetal specimens at 8 to 32 weeks of gestation. Immunohistochemical localization was performed with S-100 protein and protein gene product 9.5 to localize neurons. Blood vessels were localized by the presence of red corpuscles, and immunohistochemical staining with von Willebrand's factor and factor VIII. Three-dimensional computer reconstructions of the nerves, corporeal bodies, tunica and urethra of the hypospadiac and normal fetal penises were compared.

RESULTS

Except at the region of the abnormal urethral spongiosum and glans, the hypospadiac and normal penises showed no difference in neuronal innervation, corpora cavernosa and tunica albuginea architecture and blood supply. The nerves started proximally as 2 well defined bundles under the pubic rami superior and slightly lateral to the urethra. As the 2 crural bodies converged into the corpora cavernosa, the nerves diverged, spreading around the cavernous bodies up to the junction with the urethral spongiosum without remaining at the 11 and 1 o'clock positions. Along the entire shaft of the penis there were no neuronal structures at the 12 o'clock position. The most striking difference was in vascularity. In the hypospadiac penis factor VIII immunostaining revealed huge endothelial lined vascular channels filled with red blood cells. In contrast, the normal penis had well defined small capillaries around the urethra that fanned out into the glans. Vascularity was also extensive under the urethral plate. Nerve distribution in the abnormal glans was also less extensive than in the normal penis.

CONCLUSIONS

Increased knowledge of normal and hypospadiac penile anatomy with respect to the nerves, corporeal bodies, glans and vascularity is useful for the strategic design of penile reconstructive procedures.