Automatic Measurement of Ultrasound-Estimated Bladder Weight (UEBW) from Three-Dimensional Ultrasound.

Ultrasound-estimated bladder weight (UEBW) has the promise to become an important indicator for the diagnosis of bladder outlet obstruction. Our goal was to develop and evaluate an approach to accurately, consistently, conveniently, and noninvasively measure UEBW using three-dimensional (3D) ultrasound imaging. A 3D image of the bladder is acquired using a handheld ultrasound machine. The infravesical region of the bladder is delineated on this 3D data set to enable the calculation of bladder volume and the bladder surface area. The outer anterior wall of the bladder is delineated to enable the calculation of the bladder wall thickness. The UEBW is measured as a product of the bladder surface area, bladder wall thickness, and bladder muscle specific gravity. The UEBW was measured on 20 healthy male subjects and each subject was imaged several times at different bladder volumes to evaluate the consistency of the UEBW measurement. Our approach measured the average UEBW among healthy subjects to be 42 g (SD = 6 g). The UEBW was found to be fairly consistent with an average standard deviation of 4 g across a single subject at different bladder volumes between 200 mL and 400 mL. Our surface area measurements show that the bladder shape is significantly nonspherical.