Evaluating the urethral closure mechanism after pelvic organ prolapse surgery

The lifetime risk of undergoing surgery for pelvic organ prolapse (POP) is 19% for Danish women aged 80. The aim of surgery is to help the women regain their normal everyday-life activities, improving their quality-of-lives. Unfortunately, some of these women have concomitant stress urinary incontinence (SUI) and others develop de novo SUI after surgery. The association between POP and SUI is still unclear. Women with increased risk of de novo SUI can be identified by testing for occult SUI; the POP is repositioned, e.g. with a speculum, and a stress test is performed. If the test is positive, the woman has occult SUI. However, only half of all women with occult SUI actually develop de novo SUI postoperatively and therefore, the usefulness of the test has been questioned. Studies investigating how POP reduction and POP surgery affect the urethral closure mechanism have used conventional urethral pressure profilometry, a method that has shown wide overlaps in the results of women with and without SUI.
Urethral pressure reflectometry (UPR), a method that assesses the urethral closure mechanism by means of acoustic reflectometry, has proven highly reproducible in women with and without SUI. By measuring urethral opening pressure at an abdominal pressure of 50 mmH2O (PO-Abd 50), it is the only method that has succeeded in distinguishing between women with and without SUI.
The overall aim of this thesis was to evaluate the urethral closure mechanism before and after anterior and posterior colporrhaphy. Moreover, we assessed the reproducibility of UPR in women with POP, and examined the women before and after POP reduction to see if and how this particular test affected the urethral closure mechanism.
We conducted a prospective, observational study where women with anterior or posterior vaginal wall prolapse had one assessment before and one after surgery. Some of the women had an additional assessment before surgery so the reproducibility of UPR could be assessed.
We found that urethral opening pressures at rest, during squeezing and straining (PO-Abd 50) were highly reproducible. During POP reduction, resting and squeezing urethral opening pressures decreased in women with both anterior and posterior vaginal wall prolapse.
All parameters decreased after anterior colporrhaphy, especially PO-Abd 50. We also found that if preoperative PO-Abd 50 was ≤65 cmH2O, the positive predictive value for postoperative SUI was 50% and if PO-Abd 50 was ≥85 cmH2O the negative predictive value was 100%. There were no changes after posterior colporrhaphy.
In conclusion, we found that UPR is highly reproducible in women with POP. The urethral closure mechanism is deteriorated after anterior colporrhaphy, but remains unaffected after posterior colporrhaphy. We found that POP reduction weakened the urethral closure mechanism in both women with anterior and posterior vaginal wall prolapse. The test itself seems to have an impact on the urethra, and therefore, it cannot provide valid predictions of postoperative outcome. Preoperative PO-Abd 50 provides individual estimates of the risk of postoperative SUI.