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.