The length of anterior vaginal wall exposed to external pressure on maximal straining MRI: relationship to urogenital hiatus diameter, and apical and bladder location

Introduction and hypothesis In cystoceles, the distal anterior vaginal wall (AVW) bulges out through the introitus and is no longer in contact with the posterior vaginal wall or perineal body, exposing the pressure differential between intra-abdominal pressure and atmospheric pressure. The goal of this study is to quantify the length of the exposed vaginal wall length and to investigate its relationship with other factors associated with the AVW support, such as most dependent bladder location, apical location, and hiatus diameter, demonstrating its key role in cystocele formation. Methods Fifty women were selected to represent a full spectrum of AVW support. Each underwent supine, dynamic MR imaging. Most dependent bladder location and apical location were measured relative to the average normal position on the mid-sagittal plane using the Pelvic Inclination Correction System . The length of the exposed AVW and the hiatus diameter were measured as well. The relationship between exposed AVW and most dependent bladder location, apical location, and hiatus diameter were examined. Results A bilinear relationship has been observed between exposed vaginal wall length and most dependent bladder location (R 2 = 0.91, P < 0.001). When the bladder descents up to the inflection point (about 4.4 cm away from its normal position), there is little change in the exposed AVW length. With further descent, the exposed vaginal wall length increases significantly, with a 2 cm increase in exposed AVW length for every additional 1 cm of drop bladder location. A similar but weaker bilinear relationship exists between exposed AVW and apical location. Exposed vaginal wall length is also highly correlated with hiatus diameter (R 2 = 0.85, P < 0.001). Conclusion A bilinear relationship exists between exposed vaginal wall length and most dependent bladder location and apical location. It is when the bladder descent is beyond the inflection point that exposed vaginal wall length increases significantly.