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Keywords:

  • detrusor overactivity;
  • overactive bladder;
  • urodynamic study

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. References

Objective: We retrospectively evaluated the incidence of detrusor overactivity (DO) in uncomplicated overactive bladder syndrome (OAB) patients.

Methods: From December 1993 to October 2003, 139 adult patients were referred to an urodynamic clinic for urodynamic evaluation of frequency and/or urinary incontinence. Of these, 50 patients (12 males and 38 females) with urgency, without any overt pathological conditions, were retrospectively evaluated in regard to patient age, storage symptoms, urodynamic parameters, and the presence or absence of DO (DO patients or no DO patients, respectively).

Results: The overall incidence of DO was 75% (nine of 12 patients) and 36.8% (14 of 38 patients) in male and female patients, respectively. Two of nine male DO patients and five of 14 female DO patients revealed DO after provocative maneuvers. In male patients, all DO patients were OAB wet. In female patients, 13 of 14 DO patients were OAB wet (92.9%), whereas 17 of 24 no DO patients were also OAB wet (70.8%). Compared with no DO patients, female DO patients revealed statistically significant lower maximum cystometric capacity (P = 0.0139) and lower vesical compliance (P = 0.0002). Although aged 60 years or more was associated with DO in univariate analysis in female patients, any symptoms, even incontinence, were not associated with DO in both sexes.

Conclusion: It is supposed that, in contrast to male OAB, DO might not be a major underlying cause of uncomplicated female OAB.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. References

The term ‘overactive bladder’ (OAB) was defined in a recent report from the International Continence Society (ICS).1 OAB is used to describe a collection of symptoms composed of urgency, urge incontinence, frequency and nocturia.1 The implication of this definition is that the term OAB denotes a syndrome whose etiology is unknown. Generally speaking, detrusor overactivity (DO) is supposed to be a major underlying pathophysiology of OAB. However, it is not well elucidated exactly how many OAB patients actually show DO during urodynamic study (UDS). Although according to the ICS definition, urodynamic study is not required routinely to make a diagnosis of OAB, some neurologists and urogynecologists are concerned that a correct diagnosis will be missed in many patients, and they will not receive appropriate treatment because the bladder has been described as an unreliable witness.2 The aim of this study was to determine the incidence of DO in uncomplicated male and female OAB patients and to answer the following question: Do OAB symptoms represent with DO during UDS?

Patients and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. References

From December 1993 to October 2003, 1383 patients underwent UDS at an urodynamic clinic in Tsukuba University Hospital. Of these, 139 adult patients were referred for urodynamic evaluation of frequency and/or urinary incontinence. Of these, 50 patients (12 males and 38 females) who complained of urgency, did not have any overt neurological, vesical, bladder outlet and pelvic floor diseases, including stress urinary incontinence, and did not take any medication affecting the lower urinary tract function were evaluated. We retrospectively reviewed urodynamic report sheets and evaluated patients’ age, voiding frequency (≥eight voids per day), nocturia (≥ two voids per night), and symptomatic incontinence (OAB wet; at least once a day or OAB dry, respectively), first sensation (FS), maximum cystometric capacity (MCC), vesical compliance (Vcomp), and the presence or absence of DO (DO patients or no DO patients, respectively) and of leakage during UDS. Urodynamic investigations were performed according to the standards recommended by the ICS.1,3 Conventional filling cystometry was performed with patients in the supine position (Urodynamic system: UD5500 or Duet). The bladder was filled at a constant flow of 50 mL of water per minute, and intravesical pressure and intrarectal pressure were measured with an external transducer which was balanced at the level of the upper edge of the symphysis pubis. After patients denoted MCC, a series of provocative maneuvers were undertaken as follows: patients were asked to cough 10 times with maximal effort and then asked to sit and cough 10 times with maximal effort. DO was defined as the occurrence of an involuntary detrusor contraction (15 cm H2O or more) during the filling phase, either spontaneous or provoked. The results were statistically evaluated using Student’s t-test for comparison of the findings between DO and no DO patients, and for comparison between symptoms and UDS findings. Fisher’s exact probability test was performed to assess the association between age and DO, and between symptoms and DO. In female patients, logistic regression was also performed to assess if some clinical factors could predict DO. We selected age, frequency, nocturia and incontinence as factors, and did not select frequency with incontinence as a factor because including this factor made the fitting incomplete and any results could not come from the analysis. P-values less than 0.05 were considered statistically significant.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. References

The overall incidence of DO was 75.0% (nine patients) and 36.8% (14 patients) in male and female OAB patients, respectively. Two of nine male DO patients (22.2%) and five of 14 female DO patients (35.7%) revealed DO after provocative maneuvers, such as posture change or coughing. Table 1 shows comparisons between DO patients and no DO patients. All male DO patients were OAB wet and nine of 11 OAB wet patients (81.8%) had DO. In female patients, the mean age of 24 no DO patients was 53.1 years, which was somewhat, but not significantly, younger than that of DO patients (62.3 years, P = 0.0971). Thirteen of 14 DO patients (92.9%) were OAB wet, whereas 17 of 24 no DO patients (70.8%) were also OAB wet. Consequently, only 13 of 30 female (43.3%) OAB wet patients revealed DO during UDS. Compared with no DO patients, male DO patients revealed lower MCC (296.6 ± 71.8 mL vs. 396.7 ± 80.2 mL), and lower Vcomp (21.8 ± 6.0 mL/cm H2O vs. 30.7 ± 9.7 mL/cm H2O), but these differences did not reach statistical significance (P = 0.0686 for MCC, and P = 0.0831 for Vcomp). Also, compared with no DO patients, female DO patients revealed significantly lower MCC (290.4 ± 97.8 mL vs. 395.6 ± 132.2 mL, P = 0.0139), and lower Vcomp (27.3 ± 17.0 mL/cm H2O vs. 79.2 ± 45.0 mL/cm H2O, P = 0.0002). Leakage during UDS occurred in nine DO patients and in three no DO patients, but the latter occurred after Valsalva maneuvers, that is, urodynamic stress incontinence. Table 2 shows if any symptoms were associated with UDS findings. No significant association between symptoms and UDS findings was seen, except for the association between frequency plus incontinence and MCC in male patients, and frequency and MCC in female patients. We further analyzed these retrospective data to find out if clinicians could better predict DO when some clinical factors were combined with urgency. We performed univariate analysis, selecting age, frequency, nocturia and incontinence as factors. As shown in Table 3, although aged 60 years or more was associated with DO in univariate analysis in female patients, any symptoms, even incontinence, were not associated with DO in both sexes. Furthermore, as shown in Table 4, age was no longer associated with DO in multivariate analysis.

Table 1.  Comparison between DO patients and no DO patients in male and female subjects
 Age (years)OAB wet (n[%])FS (mL)MCC (mL)Vcomp (mL/cm H2O)Leak at UDS (n[%])
  1. Data indicates mean ± standard deviation. DO, patients with detrusor overactivity; FS, first sensation; MCC, maximum cystometric capacity; no DO, patients without detrusor overactivity; OAB, overactive bladder; Vcomp, vesical compliance.

Male
 DO (n = 9)62.3 ± 15.7 9 (100)151.4 ± 48.0296.6 ± 71.821.8 ± 6.02 (22.2)
 No DO (n = 3)65.3 ± 4.0 2 (66.7)155.3 ± 48.0396.7 ± 80.230.7 ± 9.70 (0)
P-value 0.7576 0.2500  0.9190  0.0686 0.0831 
Female
 DO (n = 14)62.3 ± 19.513 (92.9)116.7 ± 47.6290.4 ± 97.827.3 ± 16.99 (64.3)
 No DO (n = 24)53.1 ± 13.717 (70.8)134.5 ± 90.5395.6 ± 132.279.2 ± 45.03 (12.5)
P-value 0.0971 0.2157  0.5017  0.0139 0.0002 
Table 2.  Association between symptoms and UDS findings in male and female subjects
 FrequencyNocturiaIncontinenceFrequency + incontinence
YesNoYesNoYesNoYesNo
  1. * P = 0.0433, ** P = 0.0333. Data indicates the mean value. FS, first sensation; MCC, maximum cystometric capacity; Vcomp, vesical compliance.

Males
 n 10  2  9  3 11  1  9  3
 FS (mL)147.9175.0157.7136.7149.4186.0143.7178.7
 MCC (mL)312.9365.0319.0329.3307.2480.0294.3403.3*
 Vcomp (mL/cm H2O) 24.1 23.8 23.7 25.1 22.9 36.9 22.7 28.1
Females
 n 27 11 16 22 30  8 20 18
 FS (mL)114.7160.5139.1119.8134.5103.1117.2139.9
 MCC (mL)328.6426.4**311.9389.6376.1284.8338.6377.2
 Vcomp (mL/cm H2O) 61.8 55.8258.3 61.4 59.7 61.5 61.9 58.8
Table 3.  Results of univariate analysis in male and female subjects
Factors Females DOP-valueMales DOP-value
YesNoYesNo
  1. DO, detrusor overactivity.

Age (years)≥6010 80.026631
<60416 30 
FrequencyYes10170.634731
No 7 7 20 
NocturiaYes 7 90.339720.618
No 715 21 
IncontinenceYes13170.114920.25
No 1 7 01 
Frequency + incontinenceYes 9110.224720.618
No 513 21 
Table 4.  Results of multivariate analysis in female subjects
Factors Odds ratioP-value
Age (years)≥604.370.062
<601 
FrequencyYes1.630.571
No1 
NocturiaYes1.420.644
No1 
IncontinenceYes3.260.335
No1 

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. References

Urodynamic study has comprised an essential part of the diagnostic evaluation of patients with storage symptoms for many years. Among female OAB patients, 457 of 843 (54.2%) have DO, while only 11 of 47 (23%) females with frequency, urgency and nocturia, and only 15 of 67 (22%) females with urge incontinence have DO.4,5 Hashim and Abrams also reported that DO existed in 461 of 790 (58.4%) female OAB patients.6 This low incidence of DO in female OAB patients was compatible with our results; only 37% of OAB females had DO. Therefore, especially in females, DO might not be a major underlying pathophysiology for OAB. In the present study, symptoms were not well associated with UDS findings in female OAB patients. Surprisingly, urgency with frequency and urge incontinence were not associated with DO. Urgency with age over 60 years was associated with DO in univariate analysis, but not in multivariate analysis. The urgency symptom itself was reported to be poorly associated with objective parameters from the bladder diary and conventional filling cystometry. Rather, the frequency symptom, not the urgency symptom, is best associated with them in 95 females who underwent UDS.5 Conversely, frequency alone was reported to be a poor predictor of DO (31.4%) in female OAB patients, and having urgency, frequency and urge incontinence had the highest sensitivity in predicting DO (61.0%) in females.6 Besides these, it was reported that, overall, 682 of 822 (83%, 275 males and 547 females) patients with DO had OAB symptoms, while 453 of 1641 (27.6%) females with DO had OAB symptoms.4,6 Therefore, it seems that further studies are required to clarify the actual rate of DO in OAB, and of OAB in DO.

The present study revealed that OAB symptoms did not predict DO in both sexes, although male patients were small in number and 75% of male OAB had DO. It was reported that DO existed in 78.5% of 284 male OAB patients and that OAB was a better predictor of DO in males than in females.6 These results imply that the underlying pathophysiology of OAB might be different between males and females and that the treatment outcome of OAB should be evaluated with distinction of sex.

For now, there are many controversies about UDS in evaluating patients with OAB. Symptomatic diagnosis of OAB alone is not recommended and UDS is mandatory in the accurate management of the OAB female, while UDS should be performed only if it is going to change management.4,6 We propose that, to elucidate if DO is really responsible for their OAB symptoms, UDS should be considered in female OAB patients aged less than 60 years because only 20% of them actually had DO despite having urgency symptoms.

Why does the unexpected stable detrusor exist at UDS, especially in female OAB patients? Up to 60% of patients with stable detrusor during conventional UDS have DO during ambulatory monitoring.2 Reproducibility of DO during conventional UDS is another important issue to consider because repeat UDS does not demonstrate DO in 10% of 30 patients with DO at initial UDS.7 In some female OAB patients, urethral and/or pelvic floor problems are supposed to be major underlying causes.8,9 Although we might become aware of underlying pathophysiology with sphincter electromyography (EMG) and abdominal leak point pressure measurements during UDS, the results of sphincter EMG during filling and leak point pressure could not be accurately analyzed because the present study was retrospective in nature. Therefore, we could not ascertain the presence or absence of urethral dysfunction in our female population. Besides these, hypersensitive disorders also might be one of the underlying etiologies.10 In the present study, DO was revealed in 10 out of 27 female OAB patients with frequency, while frequency was associated with a decrease in MCC. This suggests the involvement of the bladder afferent in female OAB patients. Finally, provocative tests were thought to be important during UDS because only nine of 38 female OAB patients (23.7%) in the present study revealed DO without provocative maneuvers. From this, we recommend that provocative tests should be added during conventional UDS to detect DO when evaluating OAB patients.

Recently, urothelium-derived neurotransmitters, such as acetylcholine and adenosine triphosphate, and/or suburothelial myofibroblast have been considered to play an important role in emerging OAB symptoms via bladder afferent.11,12 However, these strictly localized pathological processes could not be detected during conventional UDS, and data about sensory function of the bladder depend on sensations reported subjectively by the patient. The problem is that objective evaluation of the sensation has not been available. In addition, the method of quantifying ‘urgency’ during UDS had not been reported while urgency was thought to be a driving component of all OAB symptoms. Novel methods for evaluating urinary sensation during UDS need to be developed because bladder afferent probably plays a role in the pathophysiology of OAB, and reproducing and quantifying ‘urgency’ is thought to be important as well as detecting DO in OAB patients.

The present study had several drawbacks. First, the study was retrospective. Second, the number of subjects analyzed, especially male subjects, was too small to perform statistical analysis. For example, this is why urgency with age over 60 years in females was associated with DO in univariate analysis, but not in multivariate analysis. Third, the follow-up data were lacking because most patients in the present study were referred to our urodynamic clinic purely for investigation. Therefore, there was not adequate information regarding whether or not urodynamic findings altered management for these patients.

Flisser and Blaivas emphasized that UDS could provide the opportunity for patients to receive a precise diagnosis and treatment based on the underlying cause, and for the physician to appreciate the subtle differences among patients and to make intelligent hypotheses that direct future research into diagnosis and treatment.2 Continuing arguments against ‘no need for UDS in OAB patients’ might prove fruitless. Rather, we need knowledge and/or evidence-based guidelines that define the OAB patients in who UDS could confer a benefit.

In conclusion, DO might be a major underlying cause in uncomplicated male OAB, while DO might not be a major underlying cause of uncomplicated female OAB, especially in young patients. We have to ascertain the role of and establish urodynamic methods for evaluating afferent from bladder/urethra, and/or the influence of pelvic floor muscle dysfunctions in female OAB. It is difficult to predict DO by symptoms, such as frequency, nocturia and/or incontinence, although in terms of OAB wet, most male patients (82%) had DO. The pathophysiology of female OAB might be different from that of male OAB. Therefore, treatment outcomes might be evaluated for males and females separately. Further prospective studies are needed to provide more information about the precise role of urodynamics for OAB patients.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Patients and methods
  5. Results
  6. Discussion
  7. References