Morphometric properties of the posterior vaginal wall in women with pelvic organ prolapse

OBJECTIVE: Our purpose was to analyze the morphometric properties of the posterior vaginal wall and compare the smooth muscle distribution in the posterior vaginal muscularis in women with and without pelvic organ prolapse. STUDY DESIGN: Specimens were taken from the apex of the posterior vaginal wall after hysterectomy from 15 women with pelvic organ prolapse and from 8 healthy control subjects. Smooth muscle cells of the posterior vaginal wall were identified by immunohistochemistry with antibodies to smooth muscle alpha-actin. Morphometric analysis was performed on histologic cross-sections of the posterior vaginal wall to determine the fractional area of nonvascular smooth muscle in the muscularis. The innervation pattern of the vaginal wall was determined by use of S100 immunostaining. Statistical comparisons between two groups were conducted by a Student t test. Comparisons between multiple groups were conducted with a one-way analysis of variance followed by a post-hoc Student-Neuman-Keuls test. RESULTS: The fractional area of nonvascular vaginal smooth muscle in the muscularis of women with posterior wall prolapse was significantly decreased compared with that of healthy control subjects. Nerve bundles were located in the deep vaginal muscularis and adventitia of the posterior vaginal wall. In women with posterior wall prolapse, nerve bundles were smaller and fewer in number. CONCLUSION: Morphologic features of the posterior vaginal wall are significantly altered in women with posterior wall prolapse compared with asymptomatic control subjects.