INVESTIGATING THE MECHANISM OF CONTINENCE AFTER POSTERIOR COLPORRHAPHY: A STUDY WITH URETHRAL PRESSURE REFLECTOMETRY.
KHAYYAMI, G. LOSE, N. KLARSKOV;
Department of Obstetrics and Gynecology, Herlev Gentofte Univ. Hosp., Herlev, Denmark.
Introduction: The prediction of de novo stress urinary incontinence (SUI) after pelvic organ prolapse (POP) surgery is an unsolved enigma. Urethral pressure reflectometry (UPR) has shown that the urethral closure mechanism is deteriorated after anterior colporrhaphy; this is most likely the cause of postoperative SUI. The preoperative value of urethral pressure during straining is a predictor of the risk of postoperative SUI (1). Studies have shown similar prevalence of SUI in women with posterior vaginal wall prolapse, which is thought to compress the urethra (2). But it is unclear whether postoperative de novo SUI is an issue in these women, as it is in women with anterior vaginal wall prolapse.
Objective: We sought to investigate the mechanism of continence in women with posterior vaginal wall prolapse before and after posterior colporrhaphy, by means of urethral pressure reflectometry.
Methods: This was a prospective, observational study where women with posterior vaginal wall prolapse were recruited from our outpatient clinic. The women were excluded if they: had concomitant vaginal wall prolapse ≥ grade two in the anterior compartment; had a history of previous POP- or SUI surgery or hysterectomy; used any medicine for urinary incontinence. All women gave their written consent. The women were examined twice; before and after posterior colporrhaphy. Visits were identical and included POP staging according to POP-Q and UPR measurements, in a supine position. UPR allows for simultaneous measurements of pressure and cross-sectional area in the urethra. A bag is connected to a 45 cm long PVC tube and inserted in the urethra. Using acoustic reflectometry, the cross-sectional area along the entire length of the urethra is measured continuously, and the opening pressure, which is the pressure needed to open the collapsed urethra, is measured. Measurements are done at rest, during squeezing and straining with simultaneous recordings of abdominal pressure. Measurements during straining are evaluated by plotting related values of urethral and abdominal pressures, creating a linear graph, a pressuregram. The slope of the line is called APIR (abdominal to urethral pressure impact ratio) and expresses how abdominal pressure affects urethral pressure. Using APIR, the opening pressure at a standardized abdominal pressure of 50 cmH2O, PO-Abd 50 is calculated. We expected a 10 cmH2O decrease in PO-Abd 50 to be clinically relevant. With no information regarding the standard deviation (SD) of PO-Abd 50, SD was set to 18. With a power of 80% and α of 5%, a sample size of 26 was required. Alongside this study, a study on the reproducibility of UPR in women with POP was done (3); in this study the SD was 7.9. Since updated calculation with the new SD revealed a power of 99.9% with the 17 included patients, inclusion was stopped. Pre- and postoperative parameters were compared with paired t-tests and p-values <0.05 were considered statistically significant.
Results: Our study group consisted of 17 women with posterior vaginal wall prolapse grade ≥ 2 with a mean age of 58 (34-77) years. Twelve were postmenopausal, and nine of them used local estrogen therapy. Median parity was two (1-4). The women were examined at a median of 17 (7-83) days before surgery and 53 (42-172) days after surgery. All women underwent posterior colporrhaphy: seven had concomitant perineorrhaphy. There were no other concomitant procedures. The table shows the changes in parameters before and after posterior colporrhaphy.
Conclusions: The urethral closure mechanism is unchanged after posterior colporrhaphy. The mechanism of continence is clearly not affected in the same way after a posterior colporrhaphy as it is after an anterior colorrhaphy. This study does not support the theory of the posterior prolapse masking SUI.
References: 1. Neurourol Urodyn. 2016 Aug 1;35(S4):S1-471 2. J Urol. 2004 Mar;171(3):1021-8 3. Int Urogynecology J. 2016 Nov 8, DOI:10.1007/s00192-016-3187-1
Parameters before and after posterior colporrhaphy
PO-Abd 50, cmH2O
The numbers are reported as means. PO-rest: opening pressure at rest, PO-squeeze: opening pressure during squeezing, PO-Abd 50: opening pressure at an abdominal pressure of 50 cmH2O, APIR: abdominal to urethral pressure impact ratio.