Is the Severe Stress Urinary Incontinence with Hypotonic Urethra Due to Destruction of Elastic Fibers? An Electron-Microscopical Study

Abstract

Purpose: Changes in structural support of the urethra and bladder neck have been proposed to be important factors in the pathogenesis of urinary stress incontinence. In this context, we investigated the elastic fibers of the periurethral area in incontinent women with normotonic and hypotonic urethra under an electron microscope. The exact localization and morphological structure of these fibers, their relationship to other connective tissue components as well as their possible role in the development of stress urinary incontinence were characterized. Material and Methods: We studied the periurethral connective tissue using electron microscopy. Small specimens of periurethral connective tissue were obtained by dissection during a TVT procedure in 34 urinary stress incontinent postmenopausal women with a normotonic urethra and 9 urinary stress incontinent postmenopausal women with a hypotonic urethra. Ultrathin sections were stained with uranyl acetate/lead citrate and tannic acid and were examined in a transmission electron microscope. Results: The constituent parts of the system of elastic fibers were found within the periurethral connective tissue of all stress-incontinent women in the study. In the samples taken from stress incontinent women with a normotonic urethra, these intact elastic fibers were closely connected with collagen fibers, smooth muscle cells and fibrocytes. In contrast, in the samples taken from stress incontinent women with a hypotonic urethra we detected irregular fragmented distribution of the elastin within the tissue. Conclusion: We assume that these structural changes lead to functional consequences, like diminished tissue extensibility and loss of stability surrounding the female urethra. These altered connective tissue properties may affect the mechanism of urethral closure under stress (e.g. coughing) and therefore contribute to the occurence of SUI with a hypotonic urethra.