Calculating bladder volume on ultrasound is a standard medical imaging technique for determining the amount of urine in the bladder. The ellipsoid formula is the most often used method for calculating bladder volume on ultrasound. This formula assumes the bladder has an ellipsoid shape, which is about egg-shaped.
The sonographer must collect three measurements of the bladder on ultrasound to compute bladder volume using the ellipsoid formula: length, width, and depth. Typically, these measurements are taken in the transverse, sagittal, and coronal planes.