A Proposed Method for Measuring the Volume of the Expanded Bladder by Ultrasonography

In the present study, upon a perceived urinary urgency, the bladder volume (BV) of six male university students was measured using ultrasonography (US). Immediately after imaging, each subject discharged all urine present in his bladder and the discharged urine volume (UV) was measured. The BV was calculated using US images with the conventional method and compared with the actual discharged UV. The regression coefficient of the relationship between the discharged UV and US-calculated BV differed relative to the amount of urine in the bladder. We hypothesized that this difference existed because the conventional method assumes that the shape of the bladder is ellipsoid. To prove this hypothesis, 12 US images of a fully expanded bladder were obtained from various angles using US. The shape of the bladder model created from the 12 US images resembled a rectangle or a quadrangular pyramid. For these reasons, the shape of the bladder should not be assumed to be ellipsoid when calculating the volume of a fully expanded bladder with a sufficient UV by US. Therefore, it is necessary to develop a new method to calculate the BV with a sufficient UV by US.