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Keywords:

  • overactive bladder;
  • urgency;
  • measurement of symptoms;
  • frequency;
  • incontinence

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. UNDERSTANDING ‘URGE’ AND DEFINING URGENCY
  5. THE URGENCY MODEL
  6. CURRENT TOOLS TO MEASURE URGENCY
  7. CONCLUSIONS
  8. CONFLICT OF INTEREST
  9. REFERENCES

OBJECTIVE

To review the concept of urinary urgency and its practical measurement in clinical trials, and advance the hypothesis that while urge is experienced by normal people, urgency is always pathological.

METHODS

According to the International Continence Society (ICS) definition, urgency is the primary symptom of the overactive bladder (OAB) syndrome, but in clinical trials there are inconsistencies in both the definition and assessment of urgency. We searched the PubMed and BIOSIS databases for publications and abstracts related to the clinical assessment of urgency in patients with OAB.

RESULTS

The differentiation of urgency from the normal physiological desire to void is discussed. In clinical studies of OAB, urgency has been measured both qualitatively and quantitatively. Existing qualitative assessment scales for urgency are deficient in accuracy, validation or both, and are largely inconsistent with the currently accepted ICS definition of urgency. The quantitative assessment of urgency by diary entry has been validated and may be the most accurate, reproducible and clinically meaningful method available for measuring this variable.

CONCLUSION

Based on the existing ICS definition of urgency as ‘a compelling desire to pass urine that is difficult to defer’, the concept of qualitative assessment of urgency may be flawed.


Abbreviations
OAB(S)

overactive bladder (syndrome)

QoL

quality of life

IUSS

Indevus Urgency Severity Scale

UPS

Urgency Perception Score

INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. UNDERSTANDING ‘URGE’ AND DEFINING URGENCY
  5. THE URGENCY MODEL
  6. CURRENT TOOLS TO MEASURE URGENCY
  7. CONCLUSIONS
  8. CONFLICT OF INTEREST
  9. REFERENCES

The term overactive bladder (OAB), first used in 1997 [1], has developed to become the OAB syndrome (OABS), a term that encompasses the collection of bladder storage symptoms (urgency, frequency, urge incontinence and nocturia) suggestive of detrusor overactivity. The first definition of OAB held that the symptoms of urgency, frequency, urge incontinence and nocturia could ‘occur singly or in combination’[2]. While descriptive, this definition was suboptimal, as individuals with a single symptom of urinary frequency could be deemed to have OAB when the underlying cause may not have been bladder-related.

The prevalence of symptoms of OAB has been established in large population-based surveys in the USA [3] and Europe [4]. Data from the NOBLE study [3] indicated that up to 60% of those with OAB did not actually have urge incontinence. From the standpoint of symptom bother, urgency, with or without the presence of urge incontinence, had a more significant impact on patient-reported quality of life (QoL) [3], but frequency alone had no significant effect on QoL until patients had > 11 voids/day [5]. It was obvious that the definition of OAB required clarification, and that this clarification needed to be based on the primary, or predominant, symptom of OAB.

In 2002, the Standardization Sub-committee of the ICS took into account the need to incorporate patient-reported symptom bother and QoL impact within the definition of OAB. They defined OABS or urgency/frequency syndrome as ‘urgency with or without incontinence, usually with frequency and nocturia’ in the absence of infection or other obvious pathology [6]. This new symptom-based terminology limited detrusor overactivity to a condition that can only be definitively diagnosed by urodynamic study.

The new definition of OAB identifies urgency as the pivotal symptom that patients must experience to have OAB, except for patients who present with no sensation (e.g. complete spinal cord injury). Indeed, only about a third of individuals with urgency have coexisting urge incontinence, but almost all have coexisting frequency (Fig. 1).

image

Figure 1. The relationship between the different symptoms of OABS. While not to scale, the figure indicates the relative magnitude of symptom prevalence and the overlap of OABS symptoms [2].

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This new ICS definition of OAB provides greater clarity, but making urgency the pivotal symptom of OAB requires that urologists can describe and measure it reliably. Integral to this process is the need to discriminate between urgency episodes, which are pathological, and the normal urge, or desire to void.

UNDERSTANDING ‘URGE’ AND DEFINING URGENCY

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. UNDERSTANDING ‘URGE’ AND DEFINING URGENCY
  5. THE URGENCY MODEL
  6. CURRENT TOOLS TO MEASURE URGENCY
  7. CONCLUSIONS
  8. CONFLICT OF INTEREST
  9. REFERENCES

Given the central importance of urgency to the definition of OAB, it is imperative that urgency itself be carefully defined. According to the ICS, urgency is ‘the complaint of a sudden compelling desire to pass urine, which is difficult to defer’[6]. This definition excludes the desire to void to avoid pain or leakage that was included in the earlier definition, but now includes an element of necessity that is not associated with voluntary voiding [2]. It is important to differentiate between ‘urge’, which is a normal physiological sensation, and urgency, which we consider pathological. Central to this distinction is the debate over whether urgency is merely an extreme form of ‘urge’. If this were a continuum, then normal people could experience urgency, but in the model we propose, urgency is always abnormal. However, patients with OAB can have both ‘urge’ and urgency, and not every micturition episode is associated with urgency. The challenge to researchers is to be able to differentiate ‘urge’ from urgency in patients with OAB and to describe urgency to such patients clearly enough for them to record it accurately in diaries.

The definition of urgency has two components: one is quantitative and identifies the episodes of urgency, which can be counted, and the other qualitative, which refers to the patient's inability to defer voiding once the sensation of urgency is perceived. In other words, urgency demands attention and action. Each element dynamically affects the patient's perception of treatment of OAB and their willingness to stay on therapy.

Thus, urgency, the sudden and compelling desire (or ‘urge’) to void, is a sensation which by its definition is episodic and maximal. Therefore, it is unnecessary to characterize this portion of the definition with measurements of intensity. The presence of a ‘sudden, compelling desire’ is similar to a light switch; it is either on or off. The need to void that accompanies urgency is quite distinct from the physiological sensation characteristic of bladder filling, which can be tolerated. This physiological sensation is defined as the ‘urge’, or desire to void. The desire to void can vary in intensity, and its measurement is of great interest in assessing symptom severity and the outcome of therapy; however, its clinical utility needs to be evaluated. Because urgency is episodic it can be quantified by counting, as is done for frequency and incontinence episodes using a voiding diary.

Figure 2 shows the schema of how ‘desire to void’ as a symptom of bladder fullness might be considered in relationship to the time of a void and hence the intervoid interval in a normal person. Filling cystometry experiments with normal subjects indicate that as the bladder fills, a reproducible series of sensations or increasing desire to void is experienced [7,8]. Their duration, intensity and frequency will be variable but will increase in relation to increasing bladder volume. Recent work has shown that the intensity of this sensation depends on bladder volume. Oliver et al.[9] allowed patients with OAB to grade ‘urge’ with a five-button keypad during filling and emptying of the bladder. ‘Urge’ scores were defined as (0) none, (1) mild, (2) moderate, (3) strong, and (4) desperate. During a pseudo-random sequence of bladder filling and emptying, urge scores were reproducible and strongly correlated with bladder volume, regardless of the direction of volume change [9]. At some point during bladder filling, based on individual circumstances at that time, a normal, controlled voluntary void will occur. The volume at which this occurs is called the functional bladder capacity. The ‘urge’ sensation is likely to be episodic but can resolve or be suppressed, and then recur before a void takes place. The ability to defer voiding is key to the definition of ‘urge’ and consequently results in a variable intervoid interval in normal individuals [10]. For example, with the same individual in the home, the functional bladder capacity might be different than at work, based on the availability of time, bathroom facilities and level of distraction.

image

Figure 2. A schematic of the relationship between bladder volume and desire to void during the normal micturition cycle. During the normal cycle, desire to void (urge) is intermittent and increases with bladder volume. The cycle terminates with a void that may or may not be associated with strong sensation.

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Figure 3a shows a schematic of the equivalent situation in a patient with OAB. Such a patient will also experience a desire to void similar to that in normal individuals, but when urgency episodes occur they are different because they persist, albeit episodically, until a void has taken place. This void can be either voluntary or involuntary (incontinence) depending on the circumstances. Urgency episodes are pathological and result in incontinence or small-volume voids, as well as a reduced intervoid interval. From the onset of the urgency episode to the void is an intrinsically short and inevitably variable time that is referred to as deferment or ‘warning time’ (Fig. 3b) [11]. Similarly, the period between successive episodes of urgency can be measured (the refractory or urgency-free period; Fig. 3b). It is becoming apparent that the term ‘urge incontinence’ has been misleading and has hampered thinking in this area. We suggest that just as the term urge should in this context be replaced by the term (normal) desire to void, then logically the most accurate and comparable term should be ‘urgency incontinence’. Figure 3b is a suggested model of the effect of urgency on the micturition cycle that can generate testable hypotheses and hence advance understanding of OAB. With regard to this model, the following must be considered. What components are susceptible to intervention? Do all interventions (behavioural modification, pelvic floor contractions, biofeedback, electrical stimulation, antimuscarinic agents, drugs with other modes of action) act on this model in the same way? Will it be possible to prolong deferment time or will the goal of therapy be merely to prolong the refractory period or eliminate urgency altogether? Will this model help to define subsets of patients with OAB and give a greater insight into pathogenesis? Will it serve as a tool for determining prognosis?

image

Figure 3. (a) A schematic of the effect of urgency on the micturition cycle. During an urgency episode, the desire to void increases abruptly, resulting in a void and shortening the intervoid interval, and reducing the volume voided. Therapy can eliminate urgency episodes and thus normalize the intervoid interval. (b) A schematic of two micturition cycles terminated by voids associated with urgency episodes. A refractory period, defined as the interval between voiding and the next urgency episode, can be measured and may be affected by therapy. A warning or deferral time can also be measured as the time from the onset of urgency to voiding.

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THE URGENCY MODEL

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. UNDERSTANDING ‘URGE’ AND DEFINING URGENCY
  5. THE URGENCY MODEL
  6. CURRENT TOOLS TO MEASURE URGENCY
  7. CONCLUSIONS
  8. CONFLICT OF INTEREST
  9. REFERENCES

Figure 4 shows a schematic to describe the symptomatic pathogenesis of OAB, assuming that fluid intake remains constant. The model is predicated on the theory that patients with OAB are abnormal because they experience urgency episodes; the flowchart explains how the other symptoms of OAB are secondary to the primary symptom of urgency.

image

Figure 4. Urgency reduces the intervoid interval, defined as the time between successive voids, and thus results in a reduction of volume voided. A reduction in intervoid interval may also contribute to incontinence and nocturia, although the relationship may be less obvious due to the multifactorial nature of these symptoms.

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Given that it is not possible to defer the void after an urgency episode, urgency results in an increased frequency of micturition. Another way of stating (and measuring) this is that the intervoid interval is reduced. If fluid intake remains constant, then fluid output also remains constant. Thus, increased frequency results in reduced volume voided per micturition. Incomplete bladder emptying with resultant residual volume may further contribute to a shortened intervoid interval. In Fig. 4 these steps, which are intuitive, logical and directly related to bladder function, are labelled as ‘1’. The other symptoms of OAB that also result from a reduced intervoid interval and are not so closely related to urgency are labelled ‘2’. Incontinence occurs in only a third of subjects with OAB [3] because leakage depends on a variety of urological and non-urological factors. For example, if the patient has good pelvic floor and urethral sphincter tone, the warning time may be long enough to allow a voluntary void; conversely, incontinence may occur because of sphincteric weakness. Other significant factors include the patient's mobility, access to a toilet and other environmental factors [12]. In essence, the cause of incontinence is multifactorial and therefore its response to therapy more variable.

Nocturia is also common, but only a third of subjects with nocturia have OAB, the other causes being related to habit, drinking patterns, age, non-urological sleep disturbances, cardiovascular problems and the use of certain drugs [13]. Thus, treatment of OAB will not necessarily have a consistent effect on nocturia episodes.

Urgency can reduce the intervoid interval, defined as the time between successive voids, which in turn presumably reduces the volume voided. The reduction in intervoid interval also contributes to incontinence and nocturia, although the relationship may be less obvious because these symptoms are multifactorial.

That urgency can lead to incontinence will train the patient to void more frequently; this in turn will exacerbate urgency, resulting in a vicious cycle of worsening OAB symptoms. The model suggests that this cycle may be broken by the effective initial treatment of urgency, a hypothesis that needs to be evaluated and tested in the clinical arena.

CURRENT TOOLS TO MEASURE URGENCY

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. UNDERSTANDING ‘URGE’ AND DEFINING URGENCY
  5. THE URGENCY MODEL
  6. CURRENT TOOLS TO MEASURE URGENCY
  7. CONCLUSIONS
  8. CONFLICT OF INTEREST
  9. REFERENCES

SUBJECTIVE INSTRUMENTS

Currently, there are two subjective tools that have been designed to measure urgency, but neither accounts for the intervoid interval. Both of these tools seem to have significant flaws in their design and validation, as well as a lack of focus on the key symptom (i.e. urgency).

The Indevus Urgency Severity Scale (IUSS) is a 4-point qualitative scale that has been used to assess the severity of urgency in a clinical trial [14]. Inclusion criteria for patients in this study included ≥ 10 voids/day and ≥ one urgency incontinence episode/day. Patients were asked to rate the severity of ‘urgency’ before voiding on the following scale: 0, none, no urgency; 1, mild, awareness of urgency but easily tolerated; 2, moderate, enough urgency/discomfort that it interferes with usual activities/tasks; 3, severe, extreme urgency discomfort that abruptly stops all activities/tasks.

In this scale, categories 1 and 2 refer to urge and category 3 refers to urgency. This instrument measures a mixture of normal desire to void and urgency, and as such is both a qualitative and quantitative measure, but it fails to actually measure urgency alone. An attempt was made to provide psychometric validation of the IUSS [15], using patients with OAB and not on asymptomatic subjects. The IUSS showed only low-to-moderate correlation with urinary frequency, frequency of urinary incontinence and Incontinence Impact Questionnaire scores. This might be expected, as an urgency score will not tightly correlate with symptom variables that have a multifactorial origin (Fig. 4). There was no correlation between the IUSS and average volume voided [15]. This is a serious flaw of the instrument, as an urgency measure should closely correlate with volume voided, as reduced bladder capacity will be a direct consequence of urgency (Fig. 4). Taken together, these observations suggest that this instrument is not a robust measure of urgency. Indeed, in the reported clinical trial [14], the range of mean scores was narrow and low (1.77–1.55), suggesting that the IUSS was measuring normal desire to void rather than urgency.

The Urgency Perception Score (UPS), has been proposed as an instrument for assessing the perception of urgency in a recent clinical study [16]. Patients were asked to describe their typical response when they felt the desire to urinate. There were three possible responses to this question: (1) ‘I am usually not able to hold urine; (2) ‘I am usually able to hold urine until I reach the toilet if I go immediately; (3) ‘I am usually able to finish what I am doing before going to the toilet. The UPS, quite correctly, purports to measure the perception of urgency rather than urgency per se. However, like the IUSS it has at least one category (response 3) that appears to be inconsistent with the compelling nature of urgency as defined by the ICS [6]. Similarly, response 1 would appear to be applicable to urgency with incontinence only. Inherent in the UPS is the conceptual assumption that normal desire to void (response 3), urgency (response 2) and incontinence (response 1) constitute a continuum of severity. While this idea is intuitively appealing, there has been no evidence to support such a progression. The UPS also lacks temporal characteristics that would enhance its ability to be understood by patients. For example, ‘I am not able to hold urine’ is not a clear statement in the absence of a specified period. Not being able to hold urine for 30 min is certainly different from not being able to hold urine for 3 h.

The psychometric variables of the UPS were validated using data collected in three clinical trials [17]. Construct validity was tested by correlation of the UPS and patient voiding-diary variables. Responsiveness and discriminant validity were assessed by anova[17]. The UPS was found to be conceptually valid but to have uncertain responsiveness based on the few response options available to the patients [17]. In particular, a patient who says that he/she is usually able to finish a task before going to the toilet is given no room to improve, despite still having OAB. As such, the UPS tries to measure too many aspects of OAB and does not focus entirely on urgency. Consequently, its ability to measure urgency or its perception is limited.

One shortcoming of both subjective instruments is that they were not developed from patient perceptions of the key issues related to urinary urgency. Furthermore, as single-item scales, the measures cannot capture the broad impact of urgency and are unlikely to be as reliable or responsive to treatment-related change as a multi-item scale. Another weakness of the IUSS is that it does not appear to have been validated relative to the ideal anchoring instruments. The UPS has the additional disadvantage of having response choices that are not necessarily on the same conceptual continuum. Thus, neither the IUSS nor the UPS accurately measure the symptom of urgency, making their results inconclusive.

OBJECTIVE INSTRUMENTS

The ‘warning time’, defined as the ‘interval from first sensation of urgency to voiding’ as measured by a stopwatch, was proposed as a measure of urgency and used as the primary endpoint of a recent trial [11]. The authors noted that there was a large variation in the warning time of some individuals, and suggested that the median or minimum warning time might be more appropriate and relevant measures than mean warning time.

Although warning time is a potentially useful concept, this tool has not been validated to date. Also, the range of warning times (up to ≈ 30 min in that study) suggests that the episodes measured were not ‘difficult to defer.’ Indeed, it appears that ‘urge’ was considered synonymous with urgency. If the phraseology was changed from ‘difficult to defer’ to ‘cannot defer’, such measurements might become more reproducible. The converse of warning time may also be considered, i.e. the so-called ‘urgency free’ time or the refractory period between a void and the next onset of urgency (Fig. 3b). Further development work in this area is essential.

Patient-completed voiding diaries are commonly used as a primary tool for measuring symptoms in clinical trials of OAB. Diaries have been specifically used to record changes in the number of urgency episodes during the treatment of OAB in several recent trials [18–20]. The use of the patient-completed voiding diary for collecting both normative values of fluid intake and voiding variables in clinical trials is well accepted [21]. Recording urgency and other symptoms of OAB as variables in such diaries is less common and has received less validation. In a recent study, Brown et al.[22] examined the test-retest validity of a voiding diary specifically designed to assess symptoms of OAB, including urgency episodes, in a population of individuals who were receiving treatment for OAB or who had urge incontinence and were not receiving treatment for OAB. The test-retest reliability for OAB endpoints was acceptable, with intraclass correlation coefficients of 0.76–0.95 [22].

The convergent validity of urgency and incontinence episodes as recorded in the diary was shown by the significant correlation of diary endpoints with categorical responses to separate questions about these endpoints during the previous week [22]. The authors used interclass correlation coefficients as measures of reproducibility. They found that the measures of urgency episodes had equal or higher interclass correlation coefficients than those for urinary frequency and incontinence episodes. Thus they concluded that it was possible to measure urgency episodes in diaries. Further, they showed that a 3-day diary was as accurate as a 7-day diary for such measures [22].

CONCLUSIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. UNDERSTANDING ‘URGE’ AND DEFINING URGENCY
  5. THE URGENCY MODEL
  6. CURRENT TOOLS TO MEASURE URGENCY
  7. CONCLUSIONS
  8. CONFLICT OF INTEREST
  9. REFERENCES

The ICS has defined urgency as the primary symptom of OAB, noting it to be episodic and difficult to defer. This pathological state is in contrast to normal urge (desire) to void, which is easily suppressible and a part of normal bladder sensations that accompany filling. In this article, a hypothetical model is proposed suggesting that the relationship between urgency episode and warning (deferment) time results in a reduced intervoid interval. This cascade of events leads to the genesis of the other symptoms characteristic of OAB. Urgency can be measured quantitatively with voiding diaries, which are reliable and reproducible. Other existing subjective instruments for assessing urgency were reviewed and found to be inadequate, as they confuse the symptoms of ‘urge’ (normal desire to void) and urgency. There is obviously an essential need for any terminology to be clearly understood by both the patient and the doctor, considering the difficult and inherent limitations in being able to achieve this when dealing with a concept and symptom such as urgency. The model and observations presented here will hopefully generate scientific hypotheses that can be tested experimentally. This may in turn lead to a better understanding of the causes of OAB and hopefully more effective treatments.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. UNDERSTANDING ‘URGE’ AND DEFINING URGENCY
  5. THE URGENCY MODEL
  6. CURRENT TOOLS TO MEASURE URGENCY
  7. CONCLUSIONS
  8. CONFLICT OF INTEREST
  9. REFERENCES
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