Three new experimental models of anterior urethral stricture in rabbits

BACKGROUND: This study describes and compares three surgical procedures for the construction of urethral stricture (US) models in rabbits. METHODS: Forty adult male rabbits were allocated to four groups: 36 rabbits were randomly assigned to three experimental groups, while the remaining 4 were assigned to a sham group. The penis was separated from the rectum. Then along the ventral midline, a longitudinal penile skin incision was made while ensuring that the urethral mucosa was intact and the muscular layer was not completely incised. In group 1 (n=12), ventral semi-circumferential mucosa electrocoagulation of a 1-cm length of the anterior urethra was performed until ulceration occurred. In group 2 (n=12), the ventral urethral mucosa was incised, and electrocoagulation of the dorsal semi-circumferential mucosa was performed. In group 3 (n=12), whole-circumferential mucosa electrocoagulation was performed. In group 4 (n=4), no special treatment was performed. Four weeks later, urethrography, urethroscopy, and histological evaluation were carried out. RESULTS: The weights of the rabbits in the four groups were comparable. There was no significant difference between groups 2 and 3 with regard to operative time, but the operative time in these groups was significantly longer than that in group 1 (group 2 vs. group 1: P<0.05, group 3 vs. group 1: P<0.001). After the surgery, urinary fistula with infection occurred in one rabbit in group 1, and one rabbit died due to urethral atresia in group 3. According to the urethrography and urethroscopy findings, 9 out of 12 rabbits in group 1, 5 out of 12 rabbits in group 2, and 11 out of 11 rabbits in group 3 developed US, while no rabbits in the sham group developed US. Histopathological examination revealed injury to the urothelium, inflammatory infiltration, a decrease in the amount of blood vessels and smooth muscle fibers, and a decrease in the amount of collagen fibers. CONCLUSIONS: Compared with the semi-circumferential procedures, the whole-circumferential procedure had a higher success rate. Therefore, this procedure seems to have potential for the construction of long-segment rabbit US models.