Objective: To investigate the morphological characteristics of levator ani muscle in patients with stress urinary incontinence (SUI) or pelvic organ prolapse (POP) and to explore whether the alterations could contribute to pathogenesis of the diseases.
Methods: Biopsy specimens of levator ani muscle were obtained from 15 patients with SUI, 19 patients with POP and 3 asymptomatic controls with rectal cancer during operation. The structure of levator ani muscle was examined with routine histological techniques: HE staining, modified Gomori trichrome staining, NSE staining, ACP staining, and adenosine triphosphatase (ATPase) staining.
Results: There was no significant difference in age, parity, menopausal time, disease severity and leak point pressure between SUI patients with or without muscle fibers (P > 0.05). The muscular fiber density of levator ani muscles in SUI and POP groups was decreased, fibers were arranged in disorder and separated by large quantities of dense connective tissues with infiltrating inflammatory cells. The muscle fiber fascicles showed obvious grouped denervative atrophy, fiber type grouping and angular in shape. And also there was myopathic degeneration such as centrally located nuclei, peripheral phagocytosis and vacuolated necrosis.
Conclusions: There are both neurogenic and myopathic alterations in levator ani muscle's structure in patients with SUI and POP. The presence of both acute and chronic abnormalities indicates that the weakness of pelvic floor is a consequence of prolonged denervation.