Hypothesis / aims of study
One of etiologies of overactive bladder (OAB) in patients with pelvic organ prolapse (POP) has been considered bladder outlet obstruction. In this study, we measured variables on pelvic organ mobility (POM) evaluated by dynamic magnetic resonance imaging (dMRI) and exploratively investigated the association between those and the presence or absence of OAB and/or voiding dysfunction (VD).
Study design, materials and methods
We included 118 patients with a mean age of 60.3 years who had POP of stage II or less at rest and stage III or more when straining during dMRI. The presence or absence of OAB was diagnosed with overactive bladder symptom score, while the presence or absence of VD was determined by voiding International Prostate Symptom Score (vIPSS) ≥5 (vIPSS5), maximum flow rate (Qmax) <15 mL/s (Qmax15), and post-void residual urine volume (PVR) ≥50 mL (PVR50) [1, 2]. We divided the patients into four groups: group 1 (G1), patients with OAB and VD; group 2 (G2), those with OAB only; group 3 (G3), those with VD only; group 4 (G4), those without OAB and VD. The variables on POM were measured by dMRI at rest and during straining, including the bladder neck, the most dependent position of the bladder after straining, uterine cervix (C), and anorectal angle (AR), imaginary cardinal (iCL) as well as uterosacral (iUSL) ligaments, H as well as M-lines, the anterior vaginal wall length (AVWL), posterior urethrovesical angle (PUVA), and angle of the urethral inclination (AUI). Data are presented as mean (SD), and p<0.05 was considered statistically significant with ANOVA followed by Tukey-Kramer’s test.
Results
1. Demographics of the patients (Table 1)
About half of the patients had neither OAB nor VD determined by above criteria, and there was no significant difference in POP stage with POP-quantification system among the groups. Twenty-nine and 89 patients complained of pelvic pressure and vaginal bulge, respectively. Only three patients had diabetes. Kappa coefficient for grouping based on vIPSS5, Qmax15, and PVR50 was 0.3876 for vIPSS5 vs Qmax15, 0.4420 for vIPSS vs PVR50, and 0.4414 for Qmax15 vs PVR50.
2. OAB and VD determined by vIPSS5 (Table 2)
G1 showed significantly more uterine cervical hypermobility and greater strain on iCL and iUSL than G4. G2 had significantly higher body mass index (BMI) and greater strain on iCL and iUSL than G4. G3 had significantly and tended to have smaller strain on iUSL than G1 and G2, respectively.
3. OAB and VD determined by Qmax15 (Table 2)
G1 had significantly higher BMI and greater strain on iCL strain than G4. G2 had significantly more parity, more cervical hypermobility, a greater degree of pelvic floor ptosis at rest, and greater strain on iCL and iUSL thanG4. G3 were significantly older, had significantly less longitudinal movement in AR during straining, and greater strain on AVW than G4.
4. OAB and VD determined by PVR50 (table 2)
G2 had significantly more cervical hypermobility and greater strain on iCL and iUSL than G4, and tended to have more cervical hypermobility than G3. Moreover, G2 had a significantly greater degree of pelvic floor ptosis at rest and greater strain on iCL and iUSL than G3. G3 had significantly fewer parity than G2 or G4.
Interpretation of results
In terms of LUTS, weakness of CL and USL was potentially associated with OAB as well as the combination of OAB and VD, while cervical hypermobility was potentially associated with OAB and VD. On the other hand, those variables on POM were associated with OAB alone when VD was determined by objective measures, namely, decreased Qmax and increased PVR. In addition, in patients with VD determined by PVR50, weakness of CL and USL was significantly different between OAB and VD. Patients with OAB had more impaired pelvic floor represented by AR in VD determined by Qmax15 and PVR50. Furthermore, hyperextension of AVW was associated with lower Qmax. Not performing pressure flow study was main limitation of this study.
Concluding message
Cervical hypermobility and weakness of CL and USL might be associated with both OAB and voiding symptoms. Pelvic floor impairment might be also involved in OAB. On the other hand, the measured variables on POM associated with VD determined by Qmax and PVR were not clearly identified. The respective mechanisms for VD, as determined by symptoms, uroflow, and residual urine, might be different in patients with POP.