Mechanism of Incontinence Before and After Genital Prolapse Surgery

Aim of the project

Since year 2003, Glostrup/Herlev Hospital has devised a novel technique, urethral pressure reflectometry (UPR), for measurements of pressure and cross-sectional area in the female urethra. UPR has been able to separate continent women from women with stress urinary incontinence (SUI, defined by involuntary leakage during increased abdominal pressure). The method has been validated and used in five DMSc and Ph.D. theses and stands alone in its field. (1-5)

A great percentage of women undergoing surgery for genital prolapse (characterized by a portion of the vaginal canal protruding from the opening of the vagina) develop SUI after surgery, researchers have yet to find the answer to why this occurs. Thus, there is a great need for knowledge regarding the mechanism of continence in women with genital prolapse.

The hypothesis is that UPR may be used to uncover the changes in the female urethra before and after genital prolapse surgery, revealing significant differences in the parameters in women who develop SUI after surgery.

Background

Genital prolapse is a common problem for women. A Scottish study has revealed that 9.5 % of all women undergo genital prolapse surgery during their lives. (6) Unfortunately, SUI is frequently seen after this operation. A randomized study conducted amongst women with genital prolapse, without preoperative SUI, showed that 32 % developed SUI after the operation. (7) The sunken bladder, seen in genital prolapse of the anterior (front) part of the vagina, is believed to mask SUI as it leads to a kinking of the urethra and/or compression of the urethra and since the bladder is sewn into place during surgery, the kinking or compression is eliminated. (8) Urinary tract symptoms are traditionally associated with anterior genital prolapse; however, a Danish study has revealed that SUI is just as common in women after repair of genital prolapse of the posterior (back) part of the vagina, maybe even due to the same mechanisms (compression of the urethra). (9) Efforts have been made to predict the likelihood of a patient developing SUI after genital prolapse surgery, however, the most common test, has shown disappointing positive predictive values ranging from 23 % to 53 % and negative predictive values from 74 % to 86 %. (10;11)

A mid-urethral sling is gold standard for treatment of SUI. (12) To avoid SUI after genital prolapse surgery, some clinics choose to treat all their patients with a sling, simultaneously. However, not all patients with SUI require surgery. To avoid one patient from undergoing surgery for SUI, six to ten patients must be treated with a sling during their genital prolapse surgery. (13) A Dutch study conducted on 907 women, showed that 39 % of those women who already had preoperative SUI, actually experienced an improvement in their condition. Therefore, they believe it may be reasonable to await the effects of prolapse surgery instead of performing concomitant anti-incontinence surgery. (14) Also, the mid-urethral sling is associated with some risks and complications; a survey conducted on 809 women, showed that 20.9 % had postoperative complications, such as bladder injury and bleeding. (15) There is no international consensus on the use of mid-urethral slings in women undergoing genital prolapse surgery. (13;16-18) Therefore, there is great need for knowledge and know-how regarding the mechanism of continence in women with genital prolapse, before and after surgery.

UPR

UPR measures pressure and cross-sectional area simultaneously by means of acoustic reflectometry. A very thin and highly flexible polyurethane bag is placed in the urethra; the bag is connected to a probe by a PVC tube. A digital signal processor generates sound, which is sent from the probe into the bag. The reflections from the bag are recorded and relayed to a computer where they are converted to profiles of the urethra.

At the moment the device only exists as 3 prototypes.

Material and methods

The suitable women are expected to be included and examined over a two-year period. The participants will be informed about the study in our outpatient clinic, by a doctor. To qualify as a participant there are a set of inclusion and exclusion criteria that must be met.

With a drop-out rate of 15 %, a sample size of 30 will ensure sufficient statistical power.

Women with either anterior or posterior genital prolapse will be examined, and each group will consist of 30 women. The POP-Q system (pelvic-organ-prolapse quantification system) will be applied for grading of the genital prolapse, and the patients will be asked to complete ICIQ-SF questionnaires (International Consultation on Incontinence Questionnaire Short Form). The patients will be examined with UPR while relaxing, squeezing and straining, before and six weeks after surgery. The preoperative measurements will be conducted with and without the anterior/posterior part of the vagina held in place by a vaginal pessary. A stress test, where the women are asked to cough three times after their bladders are filled with 300 ml of saline, will also be conducted, also with and without the anterior/posterior part of the vagina held in place by a vaginal pessary.

In order to investigate the reproducibility of measurements, all preoperative examinations will be repeated in 15 women with anterior genital prolapse and 15 women with posterior genital prolapse.