Anatomical studies of the urethral plate: why preservation of the urethral plate is important in hypospadias repair

Abstract

Objective To describe the detailed anatomy of the urethral plate in relation to its controversial role in hypospadias surgery. Materials and methods A newborn penis with proximal penile hypospadias and two fetal penises with distal shaft hypospadias were included in the study; 30 normal fetal penises served as the control. Specimens were embedded in paraf®n and serially sectioned (6 mm) after formalin ®xation. Every 10th section was stained with haematoxylin and eosin.Immunohistochemical staining for nerves (S100), smooth muscles (a-actin), blood vessels (factor VIII) and epithelium (cytokeratins 7, 14 and 18) were used on selected sections, with particular attention to the urethral plate. Masson's trichrome and Sirius Red stains were used to localize collagen. Results There were extensive blood vessels, glands and smooth muscle under the urethral plate in the hypospadias specimens. These relatively well organized tissues corresponded to an abnormally formed corpus spongiosum. The glands underneath the urethral plate and adjacent to the normal urethra showed positive staining for cytokeratins 7 and 18, respectively (markers of endodermal origin) but were negative for cytokeratin 14 (a marker of ectodermal origin). Penile skin and urethral plate epithelium stained positively for cytokeratin 14 but not for cytokeratin 7 and 18. The urethral plate has a rich nerve supply, as determined by S100 staining.Collagen intensity under the urethral plate was no different from that in normal areas. Tunica albuginea stained intensely for type I and III collagen. Conclusion These results show that the urethral plate is well vascularized, has a rich nerve supply and an extensive muscular and connective tissue backing. These features may explain the lower complication rate with onlay¯aps than with tube¯aps. Therefore, from these anatomical ®ndings, we continue to advocate preservation of the urethral plate and the onlay island¯ap for hypospadias reconstruction.

Distal hypospadias: which repair?

“…In 1989, Rich et al [14] first described an incision in the glanular urethral plate to obtain a cosmetically acceptable vertical slit meatus for Mathieu repair, and this was subsequently adopted for the entire length of the urethral plate as a complement to the Thiersch-Duplay urethroplasty for distal hypospadias, by Snodgrass in 1994 [6]. The urethral plate is a well-vascularized tissue with a rich nerve supply, and an extensive muscular and connective tissue backing [15]. The TIP urethroplasty takes advantage of this extensive blood supply under the urethral plate and this probably explains the success of the procedure, as shown by the low fistula rate in the present series (3.5%) and previously (0-7%) [6,7,16,17].…”

Histopathological evaluation of the urethra after the Snodgrass operation: an experimental study in rabbits

“…Baskin et al [10] and Erol et al [11] noted that the major difference between a hypospadiac and a normal penis is extensive vascularity of the abortive urethral spongiosum and glans in the hypospadiac. This ultrastructure of the hypospadiac penis may help to explain the success of healing with no scarring after TIPU [8].…”

The buccal mucosa fenestrated graft for Bracka first stage urethroplasty: experimental study in rabbits

“…A wide variety of fl aps and grafts have been used, particularly in procedures such as complex hypospadias and urethral stenosis (1). Currently, the vast majority of techniques for hypospadias repair is based on the preservation of the urethral plate, which when intact is well vascularized, has a good nervous supply and is sustained by strong muscle and connective tissue (2,3).…”