The urodynamic study (UDS) is currently the accepted standard for characterizing bladder sensation and evaluating urgency; yet, it has many limitations including lack of standardization, non-physiological fill rates, invasiveness, and patient discomfort. We have previously published a non-invasive accelerated hydration protocol to assess bladder sensation using a sensation meter and ultrasound to bypass these limitations. The current study aimed to compare real-time bladder sensation patterns obtained from accelerated hydration to real-time bladder sensation obtained from the accepted standard, urodynamics. This comparison was studied in individuals without any symptoms of urinary urgency, both with and without the use of bladder ultrasound.

Individuals without symptoms of urinary urgency were recruited to participate in this IRB approved prospective study. Individuals who answered “never” (0) to Question 5a on the ICIq-OAB survey, “Do you have to rush to the toilet to urinate?” and ≤ 1 to all other questions on the survey were enrolled to participate in the study (n=10).
 
Participants first underwent a repeated accelerated hydration protocol performed on two separate visits one week apart. One visit was performed using serial ultrasound imaging every five minutes and ultrasound was not used on the other visit. Studies were performed at the same time of day and after consuming similar food and drink.  Participants drank 2L of Gatorade-G2® as quickly as possible and subsequently completed two fill-void cycles while recording real-time bladder filling sensation (0-100% sensation) on the sensation meter. Participants were instructed how to use the sensation meter using standardized teaching materials prior to the onset of the study. 

At a later date, participants underwent a repeat-fill urodynamic protocol. The first fill was done without ultrasound and was used to establish cystometric capacity. For this fill, the infusion rate was set at 10%/min of the maximum voided volume recorded on a three day bladder diary. The second fill was done with ultrasound (every 1 minute) with the infusion rate set at 10% cystometric capacity/min defined by the first fill. All participants recorded real−time sensation (0-100% scale) using the same sensation meter as in the hydration protocol. Therefore, our study allowed for comparison of real-time sensation during urodynamic and hydration fills with and without ultrasound in the same participants. Unless specified, all data are reported as means ± standard deviation.

Data was obtained from six men and four women aged 27.8 ± 7.4 years and with BMI of 26.4 ± 5.2 kg/m2. Real-time %sensation-%capacity curves were generated and provided a comprehensive method to compare sensation between hydration and urodynamics. The hydration and urodynamic fills without ultrasound are shown in Fig 1A. Fills with ultrasound are shown in Fig1B. No significant differences were found between hydration fill 1, hydration fill 2, and urodynamics without the use of ultrasound (Fig1A). Likewise, no significant differences were found between hydration fill 1, hydration fill 2, and urodynamics with the use of ultrasound (Fig 1B). 
Volume was measured throughout this study as well. Total bladder volumes during hydration without the use of ultrasound were 743.5 ± 213.7 mL (fill 1) and 614.1 ± 321.0 mL (fill 2). Likewise, total bladder volumes during hydration with the use of ultrasound was 689.2 ± 220.1 mL (fill 1) and 587.7 ± 341.9 mL (fill 2). Total bladder volume in urodynamics was 626.1 ± 250.9 mL (without ultrasound) and 819.1 ± 285.3 mL (with ultrasound). No significant differences were found between hydration and urodynamics performed either with or without ultrasound.

The patterns of bladder sensation measured during hydration and urodynamics were similar. This similarity occurred with or without the use of ultrasound. Likewise, data for maximum bladder volumes were also similar between hydration and urodynamics with or without the use of ultrasound.

As demonstrated in this study of normal individuals (without symptoms of urinary urgency), accelerated hydration produced similar real-time bladder sensation patterns as compared to urodynamics with or without the use of bladder ultrasound. This consistency highlights the potential value of accelerated hydration to evaluate bladder sensation and volumes in a completely non-invasive fashion, Future studies are required to see if similar sensation patterns are also identified in individuals with urgency and other forms of voiding dysfunction.