The urethral plate and the underlying tissue; a histological and histochemical study

Objective: To examine the urethral plate and the underlying tissues in children with proximal hypospadias associated with severe chordee.

Materials and methods: The urethral plate and the underlying tissue specimens were excised to correct severe chordee in 17 children with proximal and perineal hypospadias with severe chordee. The median age was 20 months (range 8-36). Sections samples were marked and examined from proximal to distal. Specimens were examined histologically using hematoxylin-eosin (H/E) and Elastic van Gieson (EvG) stain. Histochemical examination was also performed using smooth muscle actin (SMA) and factor 8 antibodies. For control, samples from four patients with hypoplastic urethra proximal to the meatus including the hypoplastic segments until the normal urethra were taken. In addition, the urethra of an adult patient with penile tumor was used as control.

Results: The average size of the 17 tissue samples was 0.5 cm × 0.5 cm x 0.3 cm in depth. There was a common pattern that was seen in all the 17 specimens with a variable degree of expression. H/E staining showed that the epithelial lining changed from pseudostratified epithelium at the proximal intact urethra to non-keratinized stratified squamous epithelium at the urethral meatus to keratinized stratified squamous epithelium distally at the urethral plate level. EvG staining showed overall very few elastic fibres that increased slightly in the distal urethral plate. SMA staining showed a circular pattern of smooth muscle cells in the proximal intact urethra that changed to a U-shaped pattern at the level of the meatus, to a triangle shaped pattern just distal to the meatus. The distal urethral plate showed an irregular, disorganized rather flat pattern of the smooth muscles. Factor 8 antibodies staining the blood spaces revealed dysplastic unorganized large blood sinusoids underneath the urethral plate that were different from normal capillaries surrounding the proximal urethra.

Conclusion: The urethral plate and the underlying tissues in patients with severe chordee have different structure from normal urethra as compared to available literature and the adult control patient. The lack of elastic fibres may help to explain the rigidity of the ventral penis causing chordee. The disorganized irregular distribution of the smooth muscle fibres is suggestive of the hypoplastic corpus spongiosum. The abnormal large blood sinusoids may explain the poor healing quality of the ventral penis in patients with perineal and proximal patients associated with severe chordee. This may explain persistent/recurrent chordee observed later in those patients with severe chordee when dorsal plication is used. The study also supports the recent trend of 2 stage procedure as a plan of management for patients with proximal and perineal hypospadias with severe chordee and excision of all the dysplastic tissues during the first operation.