James I. Gillespie, Urophysiology Research Group, The Medical and Dental School, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4BW, UK. e-mail: email@example.com
Study Type – Aetiology (case series)
Level of Evidence 4
What's known on the subject? and What does the study add?
The factors taken into consideration when determining when and where to void are poorly understood. Studies on bladder sensations, obtained during cystometry of from voiding diaries, are proving difficult to transfer to everyday experiences. There is therefore a need to explore what does influence when and where to void.
This study, using focus groups, highlights the fact that many voids are driven by behavioural factors not by sensations of desire or need to void. It is further noted that a key factor in the final decision to void is an awareness of bladder volume. The concepts of ‘cognitive voiding’ informed by ‘bladder awareness’ are introduced and, if correct, will influence the way studies are devised and interpreted to explore lower urinary tract dysfunction and pharmacotherapy.
• To investigate the inter-relationship between conscious decision-making processes and bladder sensation in determining the need, time and place to void
SUBJECTS AND METHODS
• The approach used interview focus groups and qualitative thematic analysis. In this preliminary study, 25 women were included (aged 21–90 years) meeting in groups of one to five on four occasions.
• The thematic analysis yielded six themes: temporal and cognitive maps, risk issues, habituation and opportunistic behaviour and awareness of the bladder.
• For most voids, the decision to void was not based on sensation but determined by multiple factors: personal knowledge of time of last void, anticipated time to next void, proximity of toilets, a risk assessment or habituated behaviour.
• As the bladder filled the subjects described an increasing awareness of their bladder. Such sensations were not immediately associated with desire to void. Rather, these sensations were described as influencing the cognitive processes of considering when and where to void.
• A sub-group of subjects reported little awareness as their bladder filled, experiencing only sudden strong sensations that needed immediate action for fear of leakage.
• The decision to void is primarily a cognitive process influenced by multiple elements of which bladder awareness is only one.
• Mechanisms generating awareness may be intensified or lost reflecting possible different pathological states. The importance of these observations in relation to current views of normal and abnormal voiding is discussed.
The decision to void involves considerations of time and place followed by activation of the voiding reflexes. Normally, little thought is given to these processes, but, for some, this is not the case. These individuals report an increased voiding frequency and intense sensations that need immediate action to avoid leakage: the overactive bladder symptom complex (OABSC) .
Investigations into the origin of the OABSC are now focusing on the mechanisms underlying sensation. Many studies have attempted to measure sensation using simple numerical scoring systems during cystometric investigation [2,3] or as part of a voiding diary [4–7]. Such scoring schemes are widely used and form the basis of many investigations and clinical trials. However, the basic concepts underpinning this approach have recently been criticised . It was argued that the methodology may not be appropriate, causing a degree of bias that reflects more the expectation of the observer than the true experiences of the subject .
The present study is an attempt to circumvent these problems. The objectives of this preliminary investigation were: to identify, directly from asymptomatic subjects, the key factors when deciding to ‘go to the toilet’ and to identify the importance of bladder sensation in this decision-making process.
SUBJECTS AND METHODS
The study used iterative focus group discussions involving a small random sample of the females with informed consent. None reported any underlying urinary problem. As exploration into perceived sensation is intrusive, the interview focus group method was used to circumnavigate the potential problems of imposing concepts and language. A semi-structured questioning technique was used to minimise interviewer bias with the greatest opportunity for participants to generate ideas freely and in their own words. The focus group interviews comprised of: introduction, discussions on ‘going to the toilet’, frequencies/timings, perceived sensation related to the bladder, rationale for going to the toilet, relevance of place and time of day, role of fluid intake, apparent ‘suppression’ of sensation inter alia. Once ideas were formulated, basic urological terms and definitions, e.g. ‘voiding’ were introduced. Focus group information was recorded and used for thematic analysis.
In all, 25 women took part: mean (range) 60 (21–90) years. The sample was chosen opportunistically aiming to have a broad socio-economic background. Participants met in groups of one to five on up to four separate occasions. Each session lasted for 40–60 min and was held in an neutral, non-clinical/laboratory, environment. In the first two sessions, subjects were asked about voiding frequency, voiding considerations and associated sensation. From the responses, a thematic analysis was carried out and key common factors identified. At subsequent sessions, groups were presented with the key elements of the thematic analysis and asked to discuss, confirm and develop emerging concepts. It was as a consequence of these discussions that enabled a distillation and focus to be made on the major themes in relation to voiding behaviour. The acceptance and refinement of these areas were the topics of subsequent sessions. It was clear from the outset that an association existed between bladder volume and/or time from last void and bladder sensation. From this, the concept of a volume/time–sensation curve was introduced and its validity discussed.
Based on transcripts from the initial focus group sessions several issues relating to voiding behaviour were noted (Table 1). Thematic analysis yielded six major themes relating to voiding behaviour: temporal and cognitive maps, risk issues, habituation, opportunistic behaviour and bladder awareness.
Table 1. Summary of the topics arising from the initial focus-group sessions. Column 1 indicates initial subsets that identified some initial common themes. Column 2 describes and categorises the different points and factors identified in relation to the thought processes when subjects considered the time and place of voiding. From these descriptions and categorisations the thematic analysis was constructed (see results). Column 3 summarises the comments made in relation to sensations noted or experienced by subjects who were voiding in response to the other considerations. Column 4 shows the collected and paraphrased comments of the subjects in relation to their ability to control the time of voiding and its implications for their general life considerations
2 Voiding behaviour
Precise times for voiding: e.g. before going out, before the start of an event
None or very little
Temporal and cognitive maps, retain control
Opportunistic voiding: geographical: e.g. nice toilet conveniently situated geographically
None or little
Defers later stronger urge
Opportunistic voiding: temporal nice toilet, well placed temporally
None or little
Defers later stronger urge
Opportunistic but aware of bladder, convenient local: e.g. already going to vicinity of toilet
Defers later urge
Opportunistic but aware of bladder, planned: e.g. plan to go during intermission
Retains control of situation
Strong sensation, predictable: e.g. 2 h after drinking and watching television, toilet near
Will tolerate intensity longer
Strong sensation predictable, toilet not known
Strong, exacerbated by worry
Stress can increase perceived intensity
Sudden strong sensation unpredictable when it will occur
Strong and intense, requires rapid response
Strong sensation and potential leak worry, sudden onset
Strong to painful
Urge incontinence – learn to manage
Strong sensation and potential leak worry, slow onset: e.g. lying in bed
Strong, slowly becoming painful
Can tolerate extreme intensity
The background and rationale for the individual themes are outlined below:
• Temporal maps, defined as voiding behaviour based on a subjects experience and calculation of time, were evident in all participants. Relating to strong anticipatory notions of when the next need to void would be they were based on knowledge of liquids consumed and personal experience. Voiding strategy was also anticipatory in that voiding at one time was used to defer the need to void at some point in the near future. In most cases temporal maps represented a personal strategy for voiding and were usually not informed or influenced by bladder sensation.
• Many subjects demonstrated knowledge-based cognitive maps in relation to voiding (a cognitive map representing knowledge of the location of toilets). This was not a feature of subjects at home but was extremely relevant during periods of uncertainty, e.g. when outside the domestic environment. Two aspects were noted: (i) distance and location of toilets, and, (ii) quality-based considerations (e.g. cleanliness). Voids were therefore initiated based on availability, suitability and/or geographical knowledge and typically not on sensation or need.
• Risk issues were of two broad types. Some described a personal security aspect associated with visiting certain toilets. The second issue was that of leakage, although this only occurred if subjects were away from the domestic situation or faced with an inappropriate toilet. For these the decision to void involved a temporal and geographical calculation to determine whether they could defer voiding. If the possibility of leakage persisted then using an inappropriate toilet was the only option and a coping strategy adopted. Under these circumstances more importance was placed on bladder sensations and this information was used to determine an imminent or postponable risk.
• Habituation played a major role in shaping voiding behaviour through the development of behaviours to make voiding predicable and manageable. A common example given by all participants was voiding immediately before an activity; to avoid having to void during the activity and typically were not associated with bladder sensation. Opportunism was common. Voiding was carried out when an opportunity arose, so deferring a possible situation where the need to might be problematic. Participants described this as one strategy to reduce leakage.
• All participants had some appreciation of the fullness of their bladder. Assessment of fullness was an essential component in triggering immediate behaviour or anticipating and calculating an ability to defer voiding. For most voids the decision to void was not based on sensations related to the ‘need to go’. Voiding was often initiated with little sensation.
From the initial focus group discussions it was clear that subjects had difficulty describing sensations associated with the bladder. However, ‘fullness of their bladder’ was a common theme, but such feelings were indistinct and difficult to describe. On introspection most described changes with time. Initially, after a void, there was little or no sensation. This was followed by a period of increasing ‘awareness’ that eventually developed into a strong, dominant and persistent sensation. Several subjects described these strong sensations as unchanging. If they did not void then the strong sensations became painful. Over a wide range of intensities, the sensations were described in terms of a progressively intensifying ‘awareness’. In this range, no subjects related sensations to ‘a desire to void’. Awareness was used primarily to inform decision making about voiding. It was only with strong sensations did subjects agree that these could be described as the definite ‘need to go’ to the toilet.
Thematic analyses of these sessions were used to construct a graphical representation of changing awareness and distil the language used.
Figure 1A, shows a graphical representation of the pattern of awareness. This analysis was then presented to the subjects during the next focus group session. Most subjects (17/25) agreed with the general form of an ‘awareness curve’. However, some (4/25) disagreed suggesting that the period of ‘no sensation’ was short or absent and that progressively increasing and significant sensations were there all the time. The remainder (4/25) reported that they had only weak sensations of awareness that increased imperceptibly if they postponed voiding. However, this group described a rapid development of an intense sensation and desire to go to the toilet.
Figure 1A was then re-drawn to incorporate this feedback. In the final focus group session subjects were then asked to choose from one of three broad patterns of awareness as their bladder filled (a–c: Fig. 1B). Each subject had little difficulty in choosing a curve that they thought fitted the pattern of their individual developing awareness. The consensus was also that words relating to a progressive increase in awareness were appropriate. Stronger sensations of awareness were accepted as sensations linked to predictions of time to void (sensation that will need action, sensations needing action and sensations needing immediate action). Sensations greater than this were accepted to occur but rarely and described as pain. When the progressive language was incorporated into these final graphical representations all subjects related to the terminology and reported that it was informative in relating their personal experience. It is interesting to note that ‘urge’ terminology was not prevalent in the subjects own descriptions.
Once each subject had identified their preferred curve they were asked to mark on their own curve when they thought they would normally void. They were asked to use up to 10 marks representing different voids during several days. The resulting patterns of voiding correlate well with the analysis of the initial focus group sessions, where most voids were reported to occur with little or only moderate sensations of bladder awareness. Some subjects voided at almost any sensation up to and including strong sensations. Those subjects who described little sensation but then sudden strong sensations, voided frequently with little sensation trying to avoid the extreme sensations.
Clearly, sensation plays a role in determining when and where to void. Many studies accept that sensation is the primary determinant in triggering voiding. However, the present study and a few others suggest that this is not true [10–12]. It now appears that the decision to void is taken after integrating multiple factors of which sensation is only one.
The present study focuses on a group of women who have no overt urological symptoms and who were not seeing or contemplating seeing a clinician for any lower urinary tract problems. The restriction of the group to women was done simply to facilitate free and open discussion within the sessions on matters often considered personal and difficult to discuss. Similar studies are therefore needed within a ‘normal’ male population.
Several elements have been identified that influence voiding behaviour. Most voids occur as a result of behavioural and social considerations, unrelated to sensations of ‘need’ or ‘desire’ to void. The sensations are described as awareness rather than ‘desire’ or ‘need’. If the bladder is allowed to fill to near capacity, only then are sensations heightened and described as ‘need’ or ‘desire’. For this reason it may be more appropriate to describe normal voiding behaviour as ‘cognitive voiding’. This implies that a decision to void is triggered as a result of multiple considerations and not driven by sensation alone. A conceptual model describing a possible interrelationship between cognitive processes and sensory inputs is proposed in Fig. 2.
The current views of bladder sensation are derived largely from urodynamic studies. In studies using healthy subjects, volunteers were asked to report their sensations during filling [2,3]. All subjects reported spontaneously a similar sequence of sensations: a first sensation of filling, which was vague and weak, a sensation described as a first desire to void, which could be coped with and voiding delayed; and finally a strong desire to void, which was an uncomfortable sensation demanding immediate voiding [2,3]. However, quite remarkably subjects whose bladder was not being filled could report similar patterns of sensations [13–15]. Consequently, the validity of such an approach and the language and concepts underpinning sensation have been questioned and argued to be erroneous .
Bladder sensation at the time of voiding has also been assessed using voiding diaries and numerical scales devised to quantify this. It has always been a complication and an enigma that some subjects recorded a few voids with no preceding desire to void: so called ‘convenience voids’[9–12]. The observations described here are in broad agreement with this but suggest that the incidence of these voids, not driven by sensations of ‘needing to void’, may be much greater and in fact the norm. In the present study, perhaps 60% of all voids appear to have resulted predominantly from cognitive processes based on the information given by the subjects on when they voided (Fig. 1B). Most voids appearing to be initiated with mild to clear sensations rather than sensations that would need immediate action and triggering of voids for fear of leakage.
The description of bladder sensations as ‘awareness’ may be helpful in interpreting neurophysiological data quantifying bladder afferent nerve activity. It has been argued that the afferent outflow originates from discrete systems (pain, stretch receptors, urothelial-dependent mechanisms and a motor/sensory system) and that bladder sensations are contained within this ‘afferent noise’[16–19]. Afferent noise increases progressively as the bladder fills. Therefore, there may be a direct correlation between afferent noise and awareness as the bladder fills.
However, sensations associated with filling and voiding are often described as episodic [2,20]. Afferent noise and bladder awareness are not episodic suggesting that voiding sensations are different; an idea proposed originally >60 years ago but largely overlooked . This conclusion has major implications. Sensations reported at part of voiding diaries are linked to the sensations preceding a void. Consequently, diaries may not be reporting directly bladder sensation but the processing of this information. If this is correct then it has consequences for the interpretation of data from studies using voiding diaries with sensation at the time of void as their endpoint.
Some subjects appear to lack the progressive increase in awareness. These subjects report frequent voiding, which appears to originate from their cognitive strategies to avoid intense urge sensation and incontinence. Thus, the mechanisms generating or interpreting awareness may be depressed in pathological states. A different situation may occur in some patients who have increased sensations as the bladder fills. Animal models suggest that afferent outflow may be increased in animals with a partial BOO . If this is so, then bladder awareness may play a greater role in the cognitive process underlying voiding in partial BOO. This would imply that there might be sub-types of the OABSC based on alterations in bladder awareness and cognitive strategies to cope with the respective changes.
The present study proposes a modified view of the factors involved in making the decision of ‘where’ and ‘when’ to void. If this is correct then the design and interpretation of experiments with cystometry and voiding diaries, using voiding frequency and sensation, may have to be re-evaluated. A better understanding of cognitive voiding and particularly the component related to bladder awareness may lead to greater insights into the nature and underlying causes the OABSC.