Association between Cystocele Severity and Coexistent Overactive–Underactive Bladder Syndrome: A Retrospective Analysis

Introduction

Women with lower urinary tract symptoms (LUTS) are typically placed into categories based on whether they mainly suffer from storage problems (for example, sudden urgency or leakage) or voiding problems (such as slow or incomplete bladder emptying). Nevertheless, a substantial number of patients report experiencing both sets of complaints simultaneously [1-3]. Such symptoms occur with high frequency in women following menopause [4, 5]. Clinically, they are often attributed to either overactive bladder (OAB) or underactive bladder (UAB), which correspond to storage-phase or emptying-phase disorders. Urodynamic investigations link these conditions to detrusor overactivity (DO) or detrusor underactivity (DU), respectively [6].

Uroflowmetry in healthy women without neurological issues typically reveals an immediate sharp rise to a strong peak flow at the onset of voiding, a swift return to baseline, completion of micturition within 60 seconds, and almost no residual urine. When voiding dysfunction exists, however, the tracing commonly becomes flatter and more drawn out, the time needed to reach peak flow lengthens, and the maximum flow rate drops or becomes interrupted. These changes are typical of bladder outlet obstruction or reduced detrusor strength and often leave behind a considerable volume of residual urine [7].

The simultaneous appearance of both storage and emptying symptoms in one individual has lately been labeled CUOB, standing for coexistent underactive overactive bladder [8, 9]. CUOB is recognized as a distinct clinical syndrome characterized by overlapping lower urinary tract symptoms, regardless of the exact cause or underlying process. It correlates strongly with urodynamic traces that display combined detrusor overactivity–underactivity (DOU). Even in the absence of clear urodynamic confirmation of both DO and DU, CUOB is accepted today as a true syndrome that stands apart from pure OAB or pure UAB and should not be viewed simply as the addition of the two. Multiple conditions can give rise to CUOB, among them pelvic organ prolapse, loss of neural drive, reduced blood supply, tissue scarring, and mechanical obstruction at the bladder outlet [5, 9]. The disorder is considered multifactorial, and increasing age is a key contributor due to cumulative cellular damage. Much remains unknown about its development, prevalence, and urodynamic patterns.

Recent data show that 18.8% of women seeking care for pelvic organ prolapse (POP) symptoms meet the criteria for CUOB, and the degree of alignment between this clinical diagnosis and urodynamic signs of simultaneous detrusor overactivity–underactivity (DOU) can reach 75.8% [10]. Among the mechanisms proposed for CUOB are higher urethral resistance, poorer detrusor function, or both [10, 11]. Despite growing recognition, CUOB remains an incompletely defined entity that needs a more precise classification.

The goal of the present study was to compare clinical features and urodynamic measurements in patients with CUOB according to the presence or absence of a clinically relevant cystocele.

Materials and Methods

This investigation was a retrospective cohort analysis conducted at a large tertiary teaching hospital (San Gerardo Hospital, Monza, Italy). The cohort was assembled from 2000 female patients who had received urodynamic investigations between 2008 and 2016 due to pelvic floor dysfunction (PFD) [10]. Within this pool, 369 women reported symptoms matching the definition of CUOB, whereas the other 1671 women showed no evidence of CUOB. 

All participants underwent a structured medical history interview focused on lower urinary tract symptoms (LUTS). Questions covered urgency related to overactive bladder (OAB), urge urinary incontinence (UUI), stress urinary incontinence (SUI), difficulties during voiding (VS), and feelings of vaginal bulging [12]. To gauge how patients subjectively experienced the severity of their LUTS, the International Consultation on Incontinence Questionnaire-Short Form (ICIQ-UI SF) was administered [13]. 

A specialized urogynecologist performed both the physical urogenital examination and the full urodynamic evaluation, using standardized techniques described in earlier publications [14]. During the gynecological exam, pelvic organ prolapse was staged using the Pelvic Organ Prolapse Quantification (POP-Q) system [15]. Urodynamic studies followed the International Continence Society (ICS) recommended guidelines for good urodynamic practice and terminology [16]. The primary reasons prompting urodynamic testing were stress urinary incontinence in 61.1% of cases, overactive bladder symptoms in 57.5%, and voiding problems in 35.6%, although several patients had more than one indication. 

In the filling (storage) phase, recorded measurements included bladder volume at the first sensation of desire to void and at strong desire, whether urgency occurred with or without leakage, the highest detrusor pressure during filling (PdetMax), the maximum tolerated bladder capacity, and any leakage triggered by the Valsalva maneuver. Leakage caused by raised abdominal pressure in the absence of detrusor activity was documented as urodynamic stress urinary incontinence (UD-SUI). For the voiding phase, the assessed parameters comprised peak urine flow rate, maximum detrusor pressure (Pdet) at the start and finish of micturition, detrusor pressure at the moment of highest flow (PdetQmax), and the volume of urine remaining after voiding (PVR). Voiding dysfunction was identified per ICS standards when micturition was abnormally slow or incomplete, judged by reduced flow rates or unusually large post-void residuals. A flow rate below 12 mL/s was classified as abnormally slow, and post-micturition residual exceeding 100 mL was considered positive (PPVR). Detrusor underactivity (DU) was determined using the Bladder Contractility Index (BCI) originally proposed by Abrams [17], in which a score below 100 indicated DU. 

Ethical approval for this research was granted by the Institutional Review Board of the ASST Monza Ethical Committee under Approval Code: RE-PFDs dated 11 February 2022. 

Frequencies and percentages were used to describe categorical data. Normally distributed continuous variables were expressed as mean values accompanied by standard deviation (SD). Variables with skewed distributions were summarized using the median and interquartile range. Group comparisons for categorical variables relied on the Chi-square test or Fisher’s exact test as appropriate. Differences in continuous variables were examined using the independent samples t-test or the Mann–Whitney test. Every statistical test was performed two-sided, and significance was set at p < 0.05. All calculations and analyses were executed with SPSS software (IBM SPSS for Windows, version 28, IBM Corporation, Armonk, New York, NY, USA, 2021). 

Results and Discussion

POP-Q assessment revealed that cystocele occurred at a significantly higher rate among women diagnosed with CUOB than among those without CUOB (184/369; 49.9% vs. 671/1671; 40.2%, P = 0.006). 

When stratified by POP-Q findings, 185 participants (185/369; 50.1%) were in group 1, comprising 102 women with no cystocele (grade 0) and 83 with grade I cystocele. The remaining 184 participants (184/369; 49.9%) formed group 2 and presented with grade II or III cystocele. No cases of stage IV cystocele were observed in the entire cohort. Patient age was similar across groups (61.7 ± 13 years for group 1 versus 64.7 ± 10 years for group 2; P = 0.14). Body mass index proved significantly higher in group 1 (27 kg/m² versus 25 kg/m²; P = 0.02). Prolapse risk factors, specifically parity and the highest neonatal birth weight, were elevated in group 2 (1.7 vs. 2.1, p = 0.001; 3460 g vs. 3612 g, P = 0.049) (Table 1). 

Data are presented as mean ± standard deviation or count (percentage), median, and IQR (interquartile range). Non-continuous data are shown as absolute frequency. Abbreviations: CUOB = coexistent underactive overactive bladder; BMI = Body Mass Index; ICIQ-UI SF = International Consultation on Incontinence Questionnaire—Urinary Incontinence Short Form; POP = Pelvic Organ Prolapse. 

Pelvic organ prolapse symptoms occurred 4.5 times more often in group 2 (n = 162/184; 88%) than in group 1 (n = 36/185; 19.5%, P < 0.001). Involvement of other (non-anterior) vaginal compartments in prolapse was two to three times higher in group 2, with statistical significance (P < 0.001) (Table 1). 

Complete details of all POP-Q measurements appear in Table 2. 

Note: Data are presented as median and IQR (interquartile range). Abbreviations: POP-Q = Pelvic Organ Prolapse Quantification system (centimeters); GH = Genital Hiatus; PB = Perineal Body; TVL = Total Vaginal Length; CUOB =  coexistent underactive/overactive bladder.

Stress urinary incontinence occurred more often in group 1 (131/185; 70.8% vs. 102/185; 55.4%, P = 0.002), as did urge urinary incontinence (120/185; 64.9% vs. 92/184; 50%, P = 0.004). ICIQ-UI SF scores also proved significantly higher in this group (8 vs. 5, P < 0.001).

Peak flow rate (Qmax) reached a modestly higher level in group 1 (17 mL/s vs. 15 mL/s, P = 0.008). Bladder Contractility Index (BCI) values were elevated in group 1 as well (108 vs. 96.5, p = 0.017). In contrast, weak detrusor contractions, defined as BCI < 100, were more frequent among women in group 2 (73/185; 39.5%) than in group 1 (95/184; 52.7%; P = 0.011). Detrusor pressure recorded at the point of maximum flow (Pdet-Qmax) remained the same in both groups (24 cm H2O; P = 0.278). Evaluation with the Schäfer nomogram indicated that bladder contractility was weaker in group 2 (normal versus weak contraction, p = 0.003). Furthermore, the combination of low BCI scores together with positive post-void residual volume was observed more commonly in group 2 compared with group 1 (97/184; 52.7% vs. 73/185; 39.5%, P = 0.011, and 45/184; 24.5% vs. 27/185; 14.6%, P = 0.017, respectively) (Table 3).

Note: Data are presented as mean ± standard deviation or count (percentage), median, and IQR (interquartile range). Non-continuous data are shown as absolute frequency. Abbreviations: CUOBS = Coexistent Overactive Underactive Bladder Syndrome; SUI = stress urinary incontinence; Qmax = maximal flow rate mL/s; pDet at Qmax = Detrusor Pressure at Maximum Flow; DOU = Detrusor Overactive Underactive; BOO = Bladder Outlet Obstruction; BCI = Bladder Contractility Index; PVR = PostVoid Residual; PVR% = (PVR/MCC) × 100; MCC = Maximum Cystometric Capacity; PPVR = Positive PVR (PPVR) volume. U-SUI = Urodynamic Stress Urinary Incontinence. DO in UDS—Detrusor Overactivity.