Contractilité du détrusor chez la femme menopausee: influence de l’age, de la plainte et du diagnostic urodynamique

05 juin 2021

Auteurs : Françoise A. Valentini, Brigitte G. Marti, Gilberte Robain, Rebecca Haddad, Pierre P. Nelson
Référence : Prog Urol, 2021, 7, 31, 406-413




 





Brief summary: Evaluation of detrusor contractility in elderly women with two indices (PIP1 and VBN contractility parameter k); analysis of potentially influencing factors on its value.



Introduction


Detrusor contractility assessment is an essential part of urogynecology management of patients with lower urinary tract symptoms (LUTS) [1]. In older and perimenopausal women, this evaluation is critical [2] because LUTS are highly prevalent in this age group [3].


The methods for assessing detrusor contractility are still under discussion, particularly because there is noconsensus for a definition of contractility [4]. This is mainly due to the fact that this mechanical property is partly dependent on pressure and on flow. Since the 1980s, several authors have developed contractility indices based on data from pressure flow studies (PFS) [5, 6, 7] but these first attempts were essentially proposed for evaluation of detrusor contractility in obstructed men. The Watt factor (WF) introduced by Derek Griffiths [5] is well correlated with maximum isovolumetric contraction pressure but needs sophisticated computations and has poor reproducibility. Then Werner Schafer proposed a simplified approach, the projected isovolumetric pressure (PIP), based on the linearized bladder output relation; this index obeys the formula PIP=pdet.Qmax+K*Qmax where K value is 5 cmH2 O/mL.s−1 [6]. Later Tan et al. observing that the PIP indexproposed for men led to a great overestimation of detrusor contractility in womenintroduced a modified projected isovolumetric pressure where K value is 1 cmH2 O/mL.s−1: PIP1=pdet.Qmax+Qmax [8]. PIP1 has been defined for "elderly" women (range 53-89 years old) suffering from "urge incontinence". Cut-off values for that specific group were proposed as weak for PIP1<30cm H2 O and strong for PIP1>75cm H2 O (8). Recently 3 detrusor contractility indices (PIP-detrusor coefficient (DECO)-bladder contractility index (BCI)), PIP1 and contractility parameter k from the VBN (Valentini-Besson-Nelson) mathematical model [9] have been compared for women referred for evaluation of various LUTS. The authors concluded that PIP1 and parameter k produced comparable and consistent results with the urodynamic diagnosis while PIP-DECO-BCI led to inconsistencies [10]. If PIP1 has been proposed for older women, parameter k was defined regardless of age or gender. In addition, evaluation of parameter k takes into account the bladder volume at initiation of voiding.


The main objective of this study was to determine if detrusor contractility, assessed by PIP1 and parameter k, was associated with age, main complaint and urodynamic diagnosis in a large population of post-menopausal women referred for evaluation of LUTS. The secondary objective was to investigate whether either of these two indices better identified a change in contractility parameters based on patient characteristics.


Materials and methods


Study design, setting and participants


All women aged over 65 years, referredto a tertiary physical medicine and rehabilitation department for a urodynamic study with PFS as assessment of LUTS, were consecutively included in this observational study. Women with history of diabetes mellitus or neurological disease, with a pelvic organ prolapse of stage ≥II and who were unable to void, voided by abdominal straining, had an interrupted flow, voided less than 100mL or expelled their urethral catheterduring the PFS wereexcluded.


This retrospective study was conducted in accordance with the declaration of Helsinki. The local practice of our Ethics Committee does not require a formal institutional review board approval for retrospective studies.


Urodynamic investigations


Urodynamic investigations were carried out according to the International Continence Society Good Urodynamic Practices [11], using a urodynamic unit from Laborie (Mississauga Canada). Filling cystometry was performed, with saline at room temperature at a medium filling rate of 50mL/min. Filling cystometrogram was obtained via a triple lumen urethral catheter 7F allowing for urethral pressure recording and followed by an intubated flow (IF). PFS started as the patient was given the "permission to void"; detrusor and urethral pressures and urine flow rate were recorded during the whole voiding phase.


Variables and data sources


All data were retrospectively collected from medical records. Age was considered as a categorical variable and divided in a first attempt into 5-year slots (65-69, 70-74, 75-79 and >79 years). That stratification was usable for global evaluation (age, main complaint) but detailed evaluation needed larger age intervals and 65-74 vs. ≥75 years (main complaint, urodynamic diagnosis) was chosen as most developed world countries have accepted the chronological age of 65 years as a definition of ‘elderly' or older person while in some european countries the chronological age of 75 years is a criterion for geriatric care [12]. Main complaint was assessed through history taking and defined as: stress urinary incontinence (SUI), mixed urinary incontinence (MUI), urge urinary incontinence (UUI) and OTHER (no urinary incontinence). The data from each filling cystometrogram and PFS were screened for artefacts and manually entered in the database. The study focused on detrusor contractility. According to the ICS/IUGA guidelines, the main categories of urodynamic diagnoses were bladder outflow obstruction (BOO), detrusor hyperactivity with impaired contractility (DHIC), detrusor overactivity (DO) and detrusor underactivity (DU) [13]. Some investigations were found normal (N) and other related to urethral dysfunction (intrinsic sphincter deficiency (ISD) or voiding triggered by urethral relaxation (URA)).


Criteria for urodiagnostic diagnoses were: BOO: Qmax <12mL/s and pdetQmax >25 cmH2 O [14], DO: occurrence of Non Inhibited Detrusor Contration ≥ 5 cmH2 O during filling, DHIC: same as DO during filling and underactive detrusor during voiding, DU: In absence of real consensus pdetQmax <20 cmH2 O, Qmax <15mL/s, high tmic [15], N: no symptom reproduced during the assessment, ISD: low MUCP [16], and/or positive VLPP, URA: voiding triggered by urethral relaxation.


Detrusor contractility indices PIP1and VBN parameter k, were derived from pdet.Qmax and Qmax , measured during IF. Post void residual volumes (PVR) were measured using a Bladder-scan. The initial bladder volume (Vini ) was calculated by adding the PVR to the voided volume.


Statistical analysis


Data were presented as mean±SD. Analysis of variance (ANOVA), t test, and the Chi2 test were used as appropriate. Post-hoc analysis was done to explore differences between multiple groups' means. Analyses were performed on the overall study population and stratified by age. All statistical results were considered significant at P <0.05. Statistical analyses were performed using SAS, version 5.0 (SAS Institute, Inc., Cary, NC).


Results


The studied population comprised 190 women (mean age of 74.5 years) who performed a PFS according with inclusion criteria (Table 1). The most frequent complaint was MUI (33.7%), followed by UUI (28.4%). The most common urodynamic diagnoses were ISD (23.1%) then DU and DO (each 19.5%).


Association between detrusor contractility and age


Whatever the chosen age-step, there was no significant difference between PIP1 values and k values with ageing. There was no significant association between detrusor contractility indices and age considered as a continuous or a categorical variable (Table 2).


Association between detrusor contractility and main complaint


The main complaint was statistically significantly associated with both contractility indices PIP1 and parameter k, regardless of age (Table 3: P =.0242; and P =.0430). Detrusor contractility assessed by each index was significantly higher when UUI was the main complaint vs. SUIor OTHER. One found for PIP1 UUI vs. SUI P =.0153 and UUI vs. OTHER P =.0069 and for k UUI vs SUI P =.0166 and UUI vs. OTHER (P =.0083).


When age was considered, these findings remained statistically significant only when contractility was assessed by parameter k and when UUI was the main complaint vs. OTHER in patients aged between 65 and 74 years (P =.0405).


Looking at age, significant differences in 65-74 years sub-group for UUI vs. OTHER for k (P =.0405).


In the ≥75 years sub-group there was significant differences in PIP 1 for SUI vs. MUI (P =.0267), vs. UUI (P =.0115), and for UUI vs. OTHER (P =.0034), and in k for SUI vs. UUI (P =.0245) and UUI vs. OTHER (P =.0331).


For each complaint considered, there was no significant difference in detrusor contractility (as measured by PIP1 or k) between the different age groups.


Association between detrusor contractility and urodynamic diagnosis


Urodynamicdiagnosis was significantly associated with both contractility indices PIP1 and parameter k, regardless of age (Table 4; P <0001 and P <0001, respectively). Detrusor contractility was significantly greater when BOO was diagnosed vs. DHIC, DU, ISD and URA (P <.0001 for PIP1 and k) and vs. N (P =.0018 for PIP1 and<.0001 for k), when DO was diagnosed vs. DU, ISD and URA (P <.0001 for PIP1 and k) and vs. N (P =.0005 for PIP1 and<.0001 for k), and when N was diagnose vs. URA for k (P <0001).


Detrusor contractility was significantly lower when DHIC was diagnosed vs. DO (P <.0001 for PIP1 and k) and vs. N (P =.0016 for PIP1 and<.0001 for k), when DU was diagnosed vs.ISD (P <.0003 for PIP1 and<.0001 for k) and vs. N (P <.0001 for PIP1 and k), and when ISD was diagnosed vs. N (P =.0120 for PIP1 and<.0001 for k). For each urodynamic diagnosisconsidered, there was no significant difference in detrusor contractility (as measured by PIP1 or k) between the different age groups. In the 2 age classes considered, these differences remained statistically significant, with the exception of detrusor contractility measured by kor PIP1 in patients under 75 years of age when DU was diagnosed vs. ISD or when ISD was diagnosed vs. normal findings, respectively. Other exceptions were found in patients 75 years of age and older when PIP1 measured detrusor contractility and when the following comparisons were considered: BOO vs. normal, DO vs. normal and URA, DU vs. URA and N vs. URA (Figure 1).


Figure 1
Figure 1. 

Variations of PIP1 and VBN parameter k vs. urodynamic diagnosis. BOO bladder outlet obstruction; DHIC detrusor overactivity with impaired contractility; DO detrusor overactivity; DU detrusor underactivity; ISD intrinsic sphincter deficiency; N normal; URA voiding triggered by urethral relaxation. Units: PIP1cm H2 0, k no unit. Circles PIP 1: black 65-74 years old, grey ≥75 years old. Stars parameter k: black 65-74 years old, grey ≥75 years old.





Discussion


This study evaluates the association between detrusor contractility, measured by PIP1 and VBN contractility parameter k, and age, main complaint, and urodynamic diagnosis in a large population of post-menopausal women. Another investigation is to evaluate a potential supremacy of one of these indices to identify changes in detrusor contractility in older women.


We have demonstrated that in this population of older women, age was not associated with detrusor contractility. This could be explained by the fact that the decrease in detrusor contractility in aging is greater in younger patients, especially around menopause [17]. The alteration of detrusor contractility in older women would therefore be slower. To show a significant difference, a larger number of patients would therefore be required, especially in the extreme ages. Indeed, the majority of studies showing a decrease in the effect of age on detrusor contractility had a peri-menopausal population, rarely exceeding 60 years of age [15, 18, 19].


Looking at the association between detrusor contractility indices and the main complaint, PIP1 and k gave similar results as they were significantly greater when UUI was reported. However, these associations were different in patients over or less than 75 years of age, and PIP1 was significantly associated with main complaint only in patients over 75 years of age, while k was associated with main complaint regardless of age. Complaining of UUI was associated with greater preservation of detrusor contractility, possibly related to the higher incidence of detrusor overactivity in these patients. To our best knowledge, only one study has assessed the association between symptoms and DU [15]. Nevertheless, the authors focused on voiding and post micturition symptoms rather on storage symptoms. Interestingly, they have reported that a decrease in bladder sensation was significantly associated with a greater risk of DU. These results were also reported in a study by Yang et al. [20]. We can thus hypothesize that patients with UUI, because of an increased bladder sensation, have a better contractility.


Although the SUI group of ≥75 years is small, the decrease of PIP1 and k in this group can be underlined.


In the studied population, urodynamic diagnose were statistically significantly associated with both contractility indices PIP1 and parameter k, regardless of age. Expectedly, contractility indices were significantly higher in patients with BOO compared to other urodynamic diagnoses. This confirms that these indices adequately measure detrusor contractility.


Interestingly, the values of the 2 contractility indices were almost super imposable according to the urodynamic diagnosis and by age group.


This study was the first to evaluate the role of age, main complaint, and urodynamic diagnosis on detrusor contractility in older women over 65 years of age. Detrusor contractility was assessed using indices appropriate for this specific population. Moreover, PIP1 and parameter k were easily calculated from data of PFS. The software allowing k evaluation is available on request. Main advantages of parameter k are that this index can be used for any woman and that it considers the initial bladder filling. However, some limitations restrict our study's interpretation. First, it was a single-centre observational study, with retrospective data collection and the present report is flawed by the biases inherent to this study design. Second, selection biases were possible because of the mono-centric patients' inclusion. Nevertheless, we attempted to reduce this bias by consecutively include the patients in this analysis and to exclude specific population as patients with neurological diseases, diabetes mellitus and prolapse of>II grade. Furthermore, we found a prevalence similar to other studies of DU [21] and MUI was the most frequent complaint, as usually reported in older women [8]. Third, there are limitations to the use of parameter k as a detrusor contractility index, and those are primarily related to the voiding performance. As already alluded to, a non interrupted flow and no significant abdominal straining are required to accurately calculate a detrusor contractility index. Although these two conditions were applied in the mathematical computation of the k index, to our best knowledge they have not been evaluated in the development of the PIP1 index. Fourth, if the anticholinergic load (not measured in this study) had a role to play, it was only as a mediating factor and therefore taking it into account in the analysis exposed a risk of overfitting. Lastly, the use of a nomogram deduced from the VBN model could be perceived as a limitation. However, the associated software in Excel is easy to use and can be obtained (with instructions) on request from its authors (favalentini@gmail.com).


Conclusion


PIP1 and VBN contractility parameter k are indices allowing an easy evaluation of detrusor contractility. If the decrease of bladder function is a significant characteristic of a population of older women over 65 years old, there is no significant evolution of the value of indices for detrusor contractility with ageing whatever the complaint or the urodynamic diagnosis. None of these indices has predominance and both can be used for evaluation of detrusor contractility. Further studies are needed to assess the role of other factors on detrusor contractility like comorbidities, medications or duration of bladder overactivity or obstruction.


Funding


Not applicable.


Disclosure of interest


The authors declare that they have no competing interest.




Table 1 - Patients characteristics.
  Total (Nbr=190) 
Age, years  74.9 (6.5) 
65-69  51 (26.8) 
70-74  52 (27.4) 
75-79  46 (24.2) 
≥80  41 (21.6) 
Main complaint   
Stress urinary incontinence  30 (15.8) 
Urge urinary incontinence  54 (28.4) 
Mixed urinary incontinence  64 (33 .7) 
Others  42 (22.1) 
Detrusor contractility indices   
PIP1, cmH2 33.2 (13.6) 
.256 (.264) 
Urodynamic diagnosis   
Normal  30 (15.8) 
Detrusor Overactivity  37 (19.5) 
Detrusor Underactivity  37 (19.5) 
DHIC  14 (7.4) 
Bladder Outflow Obstruction  16 (8.4) 
Voiding triggered by urethral relaxation  12 (6.3) 
Intrinsic sphincter deficiency  44 (23.1) 



Légende :
Continuous variables are expressed as mean (standard deviation); Categorical variables are expressed as Nbr (%). Combined urodynamic diagnosis could only be evocated in 9% of patients with intrinsic sphincter deficiency (ISD-DU). No combined diagnosis for patients diagnosed as bladder outflow obstruction and voiding triggered by urethral relaxation.



Table 2 - Value of tested indices vs. age.
Age  65-69 y (N =51)  70-74 y (N =52)  75-79 y (N =46)  >79 y (N =41)  P  
PIP1  34.09±13.15  30.50±10.40  33.95±10.50  30.00±11.41  n.s. 
0.272±0.299  0.191±0.239  0.284±0.213  0.227±0.254  n.s. 
PIP1  32.28±11.92  32.09±11.05   
0.231±0.272  0.257±0.234   



Légende :
Units: PIP1cm H2 O, k no unit.



Table 3 - Association between main complaint and detrusor contractility indices, in the overall study population and according to age.
    SUI  MUI  UUI  Other  P  
Whole studied population  Nbr (%)  30 (15.8)  64 (33 .7)  54 (28.4)  42 (22.1)   
  PIP1  30.00±11.18  33.15±12.11  37.53±17.99  29.94±9.74  0.0242 
  0.181±0.227  0.248±0.275  0.314±0.260  0.181±0.210  0.0430 
65-74 years  Nbr (%)  21 (20.4)  24 (23.3)  34 (33.0)  24 (23.3)   
  PIP1  32.05±10.40  33.03±14.87  34.06±12.13  29.21±9.42  0.2741 
  0.201±0.215  0.223±0.322  0.313±0.281  0.163±0.236  0.2791 
≥75 years  Nbr (%)  9 (12.0)  40 (53.3)  20 (26.7)  18 (24.0)   
  PIP1  24.78±14.89  33.62±10.57  35.80±10.09  28.19±9.11  0.0931 
  0.133±0.259  0.264±0.247  0.344±0.223  0.182±0.145  0.1992 



Légende :
SUI stress urinary incontinence; MUI mixed urinary incontinence; UUI urge urinary incontinence; OTHER lower urinary tract dysfunction without incontinence.



Table 4 - Association between urodynamic diagnosis and detrusor contractility indices, in the whole studied population and according to age.
    BOO  DHIC  DO  DU  ISD  URA  P  
Whole studied population  Nbr (%)  16 (8.4)  14 (7.4)  37 (19.5)  37 (19.5)  44 (23.1)  30 (15.8)  12 (6.3)   
  PIP1  46.47±12.38  25.22±7.94  45.33±17.01  21.19±6.00  29.81±8.83  36.14±7.37  29.33±6.76  <0.0001 
  0.527±0.230  0.107±0.128  0.540±0.195  0.013±0.094  0.119±0.153  0.309±0.117  0.102±0.176  <0.0001 
65-74 years  Nbr (%)  8 (7.8)  5 (4.8)  18 (17.5)  25 (24.3)  19 (18.4)  19 (18.4)  9 (8.7)   
  PIP1  46.81±13.37  22.02±9.87  49.99±21.31  22.13±5.90  30.21±7.53  36.23±7.04  29.14±7.80  <0.0001 
  0.568±0.300  0.020±0.119  0.578±0.188  0.007±0.094  0.095±0.157  0.307±0.109  0.103±165  <0.0001 
≥75 years  Nbr (%)  8 (9.2)  9 (10.4)  19 (21.8)  12 (13.8)  25 (28.7)  11 (12.6)  3 (3.4)   
  PIP1  46.12±12.24  27.00±6.66  40.92±10.39  19.24±5.99  29.51±9.85  35.97±8.26  29.90±1.02  <0.0001 
  0.486±0.139  0.156±0.110  0.504±0.199  0.025±0.098  0.137±0.150  0.314±0.136  0.097±0.248  <0.0001 



Légende :
Continuous variables are expressed as mean (standard deviation); Categorical variables are expressed as Nbr (%); BOO: bladder outflow obstruction; DHIC: detrusor overactivity with impaired contractility; DO: detrusor overactivity; DU: detrusor underactivity; ISD: intrinsic sphincter deficiency; N: normal urodynamics; URA: voiding triggered by urethral relaxation. Combined urodynamic diagnosis could only be evocated in 9% of patients with ISD (ISD-DU). No combined diagnosis for patients diagnosed as BOO and voiding URA.


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