Anatomical and Histological Examination of the Porcine Vagina and Supportive Structures: In Search of an Ideal Model for Pelvic Floor Disorder Evaluation and Management

Objective: The objective of the study was to examine the anatomy and histology of the swine vagina and adjacent supportive structures in comparison to human tissues to determine the potential utility of this model for pelvic floor disorder evaluation and management. Methods: This is a descriptive study of the gross anatomy and histology of the swine vagina, uterosacral ligament, cardinal ligament, and rectovaginal space. Tissue was collected from 6 different sites in each of the 6 animals, processed, and stained with hematoxylin-eosin, Masson trichrome, and van Gieson and evaluated by both gynecologic and veterinary pathologists. Results: Porcine tissues were similar to the human vagina and supporting structures. The origin, insertion, and course of the uterosacral and cardinal ligaments appeared similar to those in humans. Histologically, both the porcine and human vagina and rectum consist of a mucosal, muscular, and adventitial layers. The swine vaginal smooth muscle is arranged in an inner circular and outer longitudinal manner. Collagen, elastin, and smooth muscle were identified in 5 sites. Collagen was highest in the cardinal compared with the uterosacral ligament (P = 0.03), whereas elastin was highest in the uterosacral ligament. The vaginal epithelium measured approximately 40 mu m at the vaginal cuff and 50 to 200 Km at anterior and posterior vagina. The swine vagina appeared thinner and contained less elastin. The rectovaginal region contained a smooth muscle layer leading to a thin adventitial layer. Conclusions: The swine vagina and adjacent supportive structures appear to be grossly and histologically similar to human vaginal anatomy, and these similarities could lead to further investigation of the porcine model in the study of pelvic support and support disorders.