A psychophysical study of discomfort produced by repeated filling of the urinary bladder

Psychophysical studies were performed in 10 healthy, female volunteers using urinary bladder distension (UBD) as a visceral stimulus. Stimulus methodology was similar to that used clinically for obtaining cystometrograms with a fixed-rate (100 cc/min normal saline) filling of the urinary bladder, occasional pauses and simultaneous measure of bladder pressure using a catheter-transducer assembly. During bladder filling, subjects were asked to report sensations by verbal report and by using an electronic, hand-held, visual-analog-scale device. Sensations evoked by UBD were generally localized to the suprapubic region. UBD produced cardiovascular responses which increased with repeated trials. Sensation intensity increased with repeated UBDs as indicated by global pain ratings. Intravesical pressure and volume correlated with sensation intensity. The volume of distending fluid needed to produce a report of discomfort was highly variable from trial to trial and did not change significantly with repeated UBDs. The intravesical pressure which produced a report of discomfort was less variable and significantly decreased with repeated UBDs. The change in intravesical pressure and volume needed to produce discomfort was inversely correlated with initial intravesical pressure measures. Similar to findings in other organ systems, these findings demonstrate that repeated presentations of a visceral stimulus may lead to an increase in physiological and perceptual responses to pain.