An ultrasound system and method to measure an organ wall weight and mass. When the organ is a bladder, a bladder weight (UEBW) is determined using three-dimensional ultrasound imaging that is acquired using a hand-held or machine controlled ultrasound transceiver. The infravesical region of the bladder is delineated on this 3D data set to enable the calculation of urine volume and the bladder surface area. The outer anterior wall of the bladder is delineated to enable the calculation of the bladder wall thickness (BWT). The UEBW is calculated as a product of the bladder surface area, the bladder wall thickness, and the bladder wall specific gravity.