Keratinized versus non-keratinized preputial flap onlay urethroplasty: does it make any difference in the histological analysis? An experimental study in rabbits

Purpose To compare the histological characteristics of keratinized versus non-keratinized onlay island flaps in an experimental rabbit model. Materials and Methods Sixteen male rabbits were randomly allocated into two experimental groups: keratinized and non-keratinized onlay island flaps. A defect was created in the ventral aspect of the penile urethra. In the keratinized group, a longitudinal island flap was harvested from the external prepuce and rotated to cover the urethral defect. In the non-keratinized group a transverse island flap was harvested from the inner prepuce. The animals were sacrificed after 2, 4, 8 and 12 weeks. Results The flaps were viable in all animals, and no deaths were associated with the procedure. Two urethrocutaneous fistulas were identified, one in each experimental group. A similar pattern of fibrosis was identified in both groups. The keratinized epithelium of the external prepuce kept its histological aspect and keratin production. Both keratinized and non-keratinized groups presented a slight decrease on the epithelial thickness, however without a statistically significant difference between groups. Conclusions In this short-term rabbit model, we observed that the stratified squamous keratinized epithelium from the external prepuce kept its keratin production. There was no statistical influence of the flap type on the mean epithelial thickness. .

Structural alterations of foreskin caused by chronic smoking may explain high levels of urethral reconstruction failure using foreskin flaps

OBJECTIVES: The aim of the present study was to perform a stereological and biochemical analysis of the foreskin of smoker subjects. MATERIALS AND METHODS: Foreskin samples were obtained from 20 young adults (mean = 27.2 years old) submitted to circumcision. Of the patients analyzed, one group (n = 10) had previous history of chronic smoking (a half pack to 3 packs per day for 3 to 13 years (mean = 5.8 ± 3.2). The control group included 10 nonsmoking patients. Masson's trichrome stain was used to quantify the foreskin vascular density. Weigert’s resorcin-fucsin stain was used to assess the elastic system fibers and Picrosirius red stain was applied to study the collagen. Stereological analysis was performed using the Image J software to determine the volumetric densities. For biochemical analysis, the total collagen was determined as µg of hydroxyproline per mg of dry tissue. Means were compared using the unpaired t-test (p < 0.05). RESULTS: Elastic system fibers of smokers was 42.5% higher than in the control group (p = 0.002). In contrast, smooth muscle fibers (p = 0.42) and vascular density (p = 0.16) did not show any significant variation. Qualitative analysis using Picrosirius red stain with polarized light evidenced the presence of type I and III collagen in the foreskin tissue, without significant difference between the groups. Total collagen concentration also did not differ significantly between smokers and non-smokers (73.1µg/mg ± 8.0 vs. 69.2µg/mg ± 5.9, respectively, p = 0.23). CONCLUSIONS: The foreskin tissue of smoking patients had a significant increase of elastic system fibers. Elastic fibers play an important role in this tissue’s turnover and this high concentration in smokers possibly causes high extensibility of the foreskin. The structural alterations in smokers’ foreskins could possibly explain the poor results in smoking patients submitted to foreskin fasciocutaneous flaps in urethral reconstruction surgery.