Testing a new, intensified infusion-withdrawal protocol for urinary urgency provocation in brain-bladder studies

The brain's role in bladder control has become an important area of study in the last 15 years. Typically, the brain's role in urinary urgency has been studied by repeated infusion and withdrawal of fluid, per catheter, to provoke urgency sensation during a whole brain magnetic resonance imaging (MRI) scan. Since this technique generally requires a large group size, we tested a more intense infusion-withdrawal protocol in an attempt to improve signal to noise ratio and repeatability of the signal which would, in turn, allow us to further probe subtypes of urgency urinary incontinence.

A total of 12 women over the age of 60 were recruited to test a new "intense" infusion withdrawal protocol. They underwent this new protocol during a functional brain MRI scan. The primary outcome was comparison of activity within the insula, medial pre-frontal cortex and dorsal anterior cingulate cortex/supplementary motor area (dACC/SMA). Immediate test-retest repeatability was measured using intraclass correlation. Secondary exploratory evaluation of differences in the whole brain between protocols was conducted.

There was no significant difference in signal in any of the a priori regions of interest between protocols. Test-retest repeatability in the new protocol was poor compared to the original protocol, and variability was higher. Three participants were not able to tolerate the "intense" protocol.

The small improvement in signal to noise ratio of the new protocol was not sufficient to overcome the poorly tolerated intense filling protocol.