Objective
To compare bladder sensitivity between pelvic pain and pain-free patients undergoing noninvasive, controlled bladder distension via diuresis. We also sought to measure potential mechanisms underlying bladder sensitivity.
Design
prospective observational study
Setting
community teaching hospital
Population
Reproductive-age women with non-bladder chronic pelvic pain (CPP, n=23), painful bladder syndrome (PBS, n=23) and pelvic pain-free controls (n=42)
Methods
Participants were compared on cystometric capacity, pelvic floor pressure-pain thresholds (PPTs), pelvic muscle function, O’Leary-Sant bladder questionnaire, and psychosocial instruments using Wilcoxon rank-sum tests. Multivariate regression was used to identify factors underlying bladder pain phenotypes.
Main outcome measures
self-reported bladder distension pain, pelvic floor pain thresholds
Results
Participants with PBS exhibited higher bladder distension pain than those with CPP, with both groups reporting pain higher than controls (p’s <0.05). No significant associations were found between bladder distension pain and pelvic muscle structure or pain sensitivity measures. However, bladder distension pain positively correlates with both vaginal PPTs adjacent to the bladder (r=0.46), and pain with transvaginal bladder palpation (r=0.56). Pain at maximal distension was less influenced by somatic sensitivity than bladder symptoms (r=0.35 vs. r=0.59, p<0.05). Multivariate regression identified three independent components of bladder symptoms in PBS: bladder distension pain, bladder sensation, and somatic symptoms.
Conclusions
Diuresis-induced bladder pain differentiates CPP from PBS. Experimental bladder pain is not predicted by pelvic floor sensitivity. Compared to patient-reported outcomes it appears less influenced by psychological factors. Further study is needed to determine screening for experimental bladder pain sensitivity could predict future risk of PBS.