Pathomorphism of buccal grafts used in surgery of extensive bulbar urethral strictures: immunohistochemical analysis

Abstract

Introduction. The adverse effects of urine on unadapted tissues are known. This is also entirely relevant for buccal grafts used in augmentation urethroplasty, where these effects have not been thoroughly studied so far.Objective. To assess the ongoing pathomorphosis in buccal grafts used for urethral augmentation of extensive strictures in the bulbous region and to evaluate how much urine influences their histological transformation following surgery.Materials & methods. The study included 15 patients with extensive strictures of the bulbous urethra, who underwent a two-stage augmentation urethroplasty with buccal grafts. The grafts pathomorphosis was studied 6 months after the first surgery stage where urethrotomy had been performed with graft augmentation of the dorsal semicircle and the formation of distal and proximal neomeatuses. Natural urination through the latter was restored on days 14 – 20 following the surgery. During the second stage, six months later, urethral tubularisation was performed with two preliminary biopsies of the proximal and distal segments of the grafts implanted in the areas of the neomeatuses formed earlier. The distal area of the graft had no contact with urine, while this contact has occurred in the proximal segment since restoration of natural urination. In biopsy specimens, pathomorphosis of the grafts was studied using immunohistochemical markers: vimentin, clone SRL33; CD34, clone QBEnd/10; MSA HHF-35; СD3, clone LN10; Bcl-2, clone bcl-2\100\D5; CK-HMW 34BE-12.Results. It was found that inflammation was minimal in areas of grafts implanted that had no contact with urine, while in areas where such contact occurred it was verified to be pronounced even 6 months after the operation. On the submucosal level, this was manifested by an uneven arrangement of collagen fibers, a dysplastically developed vascular network, uneven proliferation of the endothelium with swelling and loss of cellular connectivity, in contrast to areas where there was no contact with urine. In such areas, the graft submucosa had a dense collagen framework with organized microvasculature and uniform epithelial surface.Conclusion. The impact of urine on buccal grafts used in augmentation urethroplasty is characterised by the disorganisation of its collagen framework, with a pronounced inflammatory component and the “reactivity” of the epithelial lining to the “toxic agent” that persists even 6 months after surgery. This may underlie the risk of a stenosis relapse in the proximal anastomosis area.