A noninvasive bladder sensory test supports a role for dysmenorrhea increasing bladder noxious mechanosensitivity

Abstract

Objective: Catheterization to measure bladder sensitivity is aversive and hinders human participation in visceral sensory research. Therefore, we sought to characterize the reliability of sonographically estimated female bladder sensory thresholds. To demonstrate this technique's usefulness, we examined the effects of self-reported dysmenorrhea on bladder pain thresholds.

Methods: Bladder sensory threshold volumes were determined during provoked natural diuresis in 49 healthy women (mean age, 24±8 y) using 3-dimensional ultrasound. Cystometric thresholds (Vfs, first sensation; Vfu, first urge; Vmt, maximum tolerance) were quantified and related to bladder urgency and pain. We estimated the reliability (1-wk retest and interrater). Self-reported menstrual pain was examined in relationship to bladder pain, urgency, and volume thresholds.

Results: Average bladder sensory thresholds (mL) were Vfs (160±100), Vfu (310±130), and Vmt (500±180). Interrater reliability ranged from 0.97 to 0.99. One-week retest reliability was Vmt=0.76 (95% CI, 0.64-0.88), Vfs=0.62 (95% CI, 0.44-0.80), and Vfu=0.63 (95% CI, 0.47-0.80). Bladder filling rate correlated with all thresholds (r=0.53 to 0.64, P<0.0001). Women with moderate to severe dysmenorrhea pain had increased bladder pain and urgency at Vfs and increased pain at Vfu (P's<0.05). In contrast, dysmenorrhea pain was unrelated to bladder capacity.

Discussion: Sonographic estimates of bladder sensory thresholds were reproducible and reliable. In these healthy volunteers, dysmenorrhea was associated with increased bladder pain and urgency during filling but unrelated to capacity. Plausibly, women with dysmenorrhea may exhibit enhanced visceral mechanosensitivity, increasing their risk to develop chronic bladder pain syndromes.

Conflict of interest statement

Disclosure: The authors report no conflict of interest.

Figures

Figure 1. Example timeline of bladder testing protocol

The events fixed in 15 minute intervals are shown in solid lines. Ultrasound scans dependent on subject descriptors of bladder capacity are shown in dashed lines. At the beginning of the study, all of the subjects voided, began hydration and underwent a baseline scan. Every 15 minutes subsequently, subjects indicated urgency and pain on a VAS scale. Once the subject had attained first sensation of bladder distension, an ultrasound scan was performed. Additional scans were performed as the subjects reached the prespecified, verbally anchored cystometric thresholds. If study was not completed by 45 and 60 minutes, the subject was instructed to drink an additional 10 oz of water at each point. The duration of the study was capped at 120 minutes.

Figure 2. Dysmenorrhea is associated with increased bladder pain during natural diuresis

Top: Box-plots (minimum, bottom quartile, median, top quartile, maximum) are shown for data that does not follow a normal distribution. A: Demographics of individual quartiles with differing levels of self-reported menstrual pain. B: Reports of bladder pain at first sensation, first urge and maximum tolerance in each individual quartile. Bottom: Bar graphs (average and standard error of the mean) are shown for C: urgency and D: sonographically measured volume at each bladder threshold. Menstrual pain was significant as a factor in bladder pain-first sensation & urge, and in bladder urgency-first sensation (p’s nd quartile.

Figure 3

Within-subjects examination of bladder pain during menses Legend: Gray lines represent subjects with severe menstrual pain (upper quartile) and black lines represent the rest of subjects in which it was possible to obtain data measurements during menses (M) and at another portion of their menstrual cycle (N). Black circles indicate median results from subjects reporting pain during diuresis during first sensation, first urge and maximum tolerance.