Effects of Training and Mechanical Force of Ultrasound on Bladder Filling: Repeatability of Oral Hydration Studies in Healthy Adults
Currently, ICS-defined verbal sensory thresholds are the only objective measures of real time bladder sensation in the micturition filling phase. A non-invasive protocol was previously developed using 3D ultrasound and a sensation meter to more completely characterize real time bladder sensation and its correlation with bladder volume/shape/rhythm. This study validates the protocol by measuring the effects of participant training and ultrasound probe pressure in oral hydration studies.
Healthy volunteers with no urinary symptoms (ICIq-OAB scores) were recruited into an oral hydration study. Throughout 2 complete fill/void cycles, the participants drank 2L Gatorade G2 and used a touch-screen sensation meter. Participants used the sensation meter to record real-time bladder sensation (0-100%). The study was repeated 3 times, once a week (Visits A, B, and C). In visits A and B, ultrasound images were obtained every 5min. The ultrasound was not used in visit C. For each 5% sensation increment, bladder volumes were calculated by measuring the bladder capacity/time (assuming constant fill rates).
10 participants (3 male/7 female) completed all visits. Fig1 shows %sensation vs. %capacity. In the group receiving ultrasound, the untrained participants (A1) had a decreased sensation (left shift) occurring mainly at low capacities (5-50%), likely representing the effect of training. With the removal of the ultrasound (C1 and C2), there is a further decrease in sensation (left shift), likely representing an additional sensation effect from the ultrasound probe.
Because both visits A and B had ultrasound, the decreased sensation (left shift) at low capacities likely represents the effects of training (Fig1, red arrow). In visit C where the ultrasound probe was withheld, there was a further decrease in sensation (left shift), likely due to the probe pressure (Fig 1, blue arrow). This validation study demonstrates that during oral hydration studies, training and ultrasound probe pressure can affect real-time bladder sensation. This will further clarify variables that influence non-invasive metrics for filling phase sensation.
Funding: Grants from the National Institutes of Health (R01DK101719) and from the Virginia Commonwealth University School of Medicine Summer Research Fellowship Program