In this original analysis, we aimed to study differences in the relationship between desire to void and voided volume between healthy adults and overactive bladder (OAB) patients. OAB patients commonly present with symptoms of urgency, defined as a sudden compelling desire to pass urine, which is difficult to defer (1), whereas healthy adults are known to show a progressive increase in desire to void (2). To gain a better understanding of voiding patterns of patients with lower urinary tract symptoms (LUTS), micturition diaries offer a highly utilized diagnostic tool enabling quantification of patient specific complaints. Based on data collected using micturition diaries patients can be categorized into different types of LUTS and different therapeutic approaches can be considered. Commonly, micturition diaries include measurements of voiding frequency and volume, and regularly volumes of consumed liquids are included as well. Previous studies aiming to differentiate OAB patients from other LUTS and healthy adults mainly looked at voiding frequency, nocturia and voided volumes. However, the diagnostic and predictive value of micturition diaries may be improved by including sensory parameters. The relationship between classically used parameters (frequency, volumes, nocturia) and desire to void has received far less attention. Since other factors than purely bladder volume influence desire to void in OAB patients (e.g. detrusor overactivity, but likely also central nervous system mechanisms of alarm falsification) we expect this will be reflected on desire to void reported on sensation related micturition diaries. We hypothesize that reported desire to void will show a stronger relationship with voided volumes for healthy adults compared to OAB patients.

After obtaining informed consent, healthy female volunteers (N=15) were asked to complete a 3-day sensation related micturition diary including measurements of voiding frequency, voided volumes, episodes of nocturia, and desire to void. We compared responses of healthy individuals with those of female OAB patients (N=15) by retrospective assessment of clinically available responses on 3-day sensation related micturition diaries from OAB patients qualifying for sacral neuromodulation. Desire to void was assessed using the 4-point Indevus Urgency Severity Scale (IUSS) (3), which ranges from 0-3.

An overview of the multiple comparison corrected (Bonferroni method) results is shown in Table 1. We found significant results for established parameters of OAB When comparing desire to void across groups. OAB patients showed a significantly higher frequency compared to healthy controls (p = 0.002), and show significantly smaller mean ( p < 0.001) and maximal (p = 0.003) voided volumes. Additionally, our data show that healthy participants are more likely to void with a desire to void level of 1 on the IUSS (p < 0.001) and OAB patients are more likely to void with a IUSS level of 3 (p < 0.001). Furthermore, when comparing mean voided volumes at IUSS 2 and 3, significantly lower volumes were seen in OAB patients compared to healthy adults (IUSS 2 p < 0.001, IUSS 3 p < 0.001). Differences in mean voided volumes between IUSS 2 and 3 were significantly larger in healthy volunteers compared to OAB patients (p = 0.042).

In addition to established OAB parameters, our data indicate that a larger percentage of voids for OAB patients is associated with high levels of desire to void reported on the IUSS (in particular IUSS 3) compared to healthy adults. In healthy adults the opposite pattern was observed. Moreover, desire to void (especially at IUSS 2 and 3) proves indicative of voided volumes in healthy volunteers, but not in OAB patients were no significant increase in volume was observed with increasing reported desire to void. Further improvement of our understanding of the relationship between sensations arising from the lower urinary tract and voided volumes may help to differentiate different subtypes LUTS patients and can improve therapeutic approaches. This knowledge may increase the diagnostic value of sensation related micturition diaries and may offer new approaches to establish and monitor therapeutic effectivity.

Here we show that desire to void (measured using the IUSS) shows different relationships with voided volumes between OAB patients and healthy adults. A stronger connection can be observed between desire to void and voided volume for healthy adults compared to OAB patients. Indicating that the desire to void sensation experienced by OAB patients is not indicative of the volume that will be voided. Adding sensation related parameters to micturition diaries, such as the IUSS, can improve the diagnostic value of micturition diaries and may offer means to further differentiate different subtypes of LUTS patients.

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Continence 7S1 (2023) 100752
DOI: 10.1016/j.cont.2023.100752