AB282. SPR-09 A method to quantify of bladder wall biomechanics using ultrasound imaging in conjunction with urodynamics

Objective: Overactive bladder (OAB) is often associated with detrusor over-activity which is characterized by biomechanical changes in the smooth muscle of the bladder wall, but there is no established method to measure these changes in vivo. This study’s goal was to develop a novel method to determine detrusor wall biomechanical parameters during urodynamics through the incorporation of abdominal ultrasound imaging.

Methods: Individuals with OAB underwent ultrasound imaging during filling. Fill rate was 10% cystometric capacity (CCap) as determined by an initial fill. Ultrasound images were obtained using a Philips Epiq 7 machine with a 1–5 MHz abdominal probe to capture midsagittal and transverse images at 1 min intervals. Using image data and vesical pressure (Pves), detrusor wall tension, stress, and compliance were calculated. From each cross−sectional image, luminal and wall areas along with inner perimeters were measured. In the sagittal and transverse planes, wall tension was calculated as Pves*luminal area, wall stress as tension/wall area, and strain as the change in perimeter normalized to the perimeter at 10% CCap. Elastic modulus was calculated as stress/strain in each direction. Patient-reported fullness sensation was continuously recorded.

Results: Data from five individuals with OAB showed that detrusor wall tension, volume, and strain had the highest correlation to continuous bladder sensation of all quantities measured. This finding demonstrates that Pves and Pdet measurements during urodynamics may not necessarily reflect the underlying state of detrusor wall tension.

Conclusions: This study demonstrates that detrusor wall tension, stress, strain, and elastic modulus can be calculated by adding ultrasound imaging to standard urodynamics. This technique may be useful in better understanding the biomechanics involved in OAB and other bladder disorders.

Funding Source(s): Research funding for this study was provided by the Virginia Commonwealth University Presidential Research Quest Fund and NIH grant R01DK101719.

Keywords: Bladder; biomechanics; ultrasound; cystometry; human