The role of tunica vaginalis graft as the dorsal component of urethra in 1-stage and 2-stage hypospadias repair: experimental study in rabbits

PurposeThe paucity of tissue for the urethroplasty in complex Hypospadias has opened a discussion and the search for alternative materials. The buccal mucosa is the most popular tissue used to date. We were interested to evaluate the use of tunica vaginalis graft as dorsal component of urethra anastomosed either to normal urethral mucosa, to a penile preputial flap and also as a graft in 2-stage Bracka strategy.Material and MethodsWe used a rabbit model and created a defect in the penile urethra and developed 3 experiments to study clinical outcome and histological healing of the neourethra with hematoxilin-eosine and Masson's trichrome staining techniques. For each experiment (n=16), 4 subgroups of sacrifice with 4 animals each were defined according to sacrifice date of 2, 4, 8 and 16 weeks. The difference of experiment 1 to 2 was that dorsal tunica vaginalis was anastomosed to normal urethra (E1) and to a transverse preputial flap (E2) whereas in experiment 3 (E3) the tunica vaginalis graft was left exposed to external environment.ResultsThe macroscopical aspect of the surgery was uneventful in E1 and E2, whereas E3 showed an edematous and inflammatory aspect with progressive and spontaneous resolution after 4 weeks. The histological analysis of the graft was very similar in both clinical situations. The aspect of a mesotelial one cellular layer of tunica was progressive replaced by a 4-5 layer cuboid-cells epithelium at 16 weeks, suggesting metaplasia, since no follicles and keratin were seen. Interestingly, the “Bracka” tunica vaginalis surgery had the same histological appearance of dorsal TV urethroplasty when anastomosed either to normal urethra or to a foreskin flap.ConclusionsThe experimental findings suggest us that tunica vaginalis may have a role in urethral reconstruction when used as a dorsal graft attached to corpora and could be used as an alternative to other recognized options such as buccal mucosa and foreskin.