Role of the pelvic floor in bladder neck opening and closure II: vagina.

The aim of the study was to examine the role of vaginal stretching during bladder neck opening and closure. The study group comprised 12 patients with GSI and 4 controls. The position of the bladder neck relative to the vagina was assessed in the resting, straining and 'squeezing' positions using video-radiological studies. Radio-opaque dye was instilled into the bladder, vagina, rectum and levator plate. Vascular clips applied to the midurethral, bladder neck and bladder base parts of the anterior vaginal wall assisted in determining differential movements of these parts of the vagina during bladder neck opening and closure. The suburethral vagina (hammock) was shown to stretch downwards and forwards during straining, and downwards and backwards during micturition. The bladder neck, upper part of the vagina and the rectum were stretched backwards and downwards in an identical manner during straining and micturition, apparently in response to backward contraction of the levator plate and downward angulation of its anterior lip. All organs were stretched upwards and forwards during 'squeezing'. The findings support the hypothesis that, during stress and micturition, selective pelvic floor contractions stretch the vagina against intact pubourethral and uterosacral ligaments to assist opening and closure of the urethra and bladder neck.