Rachel J. Bernardo1, Anna S. Nagle2, Adam P. Klausner3, John E. Speich2
Objective: Various methods are currently available to non-invasively quantify bladder volume. The goal of this project was to determine the most accurate method of quantifying bladder volume using 2D and 3D ultrasound techniques during UD.
Methods: Nine female participants with OAB underwent an extended urodynamics procedure (Laborie Aquarius XT) while ultrasound images of the bladder were obtained using a 3D 6 MHz transabdominal probe (GE Voluson E8). The bladder was filled with saline at a rate of 10% bladder capacity (based on an initial clinical fill) per minute while ultrasound images were captured once per minute. Bladder volume was estimated from 2D cross-sectional images in the sagittal and transverse planes assuming an ellipsoid geometry [equation 1, VSpheroid = (W*H*D)], assuming a shape in between an ellipsoid and a cube [equation 1, VBih =0.72*W*H*D =1.375*VSpheroid], and from the 3D ultrasound data obtained by tracing the bladder outline in six planes with GE’s 4D View software (V3D). In equations 1 and 2, W is the width (horizontal diameter) and H is the height (vertical diameter) in the sagittal direction and D is the depth in the transverse direction (horizontal diameter).
Results: VSpheroid was significantly lower than infused volume (VH2O) when compared by a paired t-test. VBih and V3D tended to be slightly larger than VH2O, but not significantly.
Conclusions: The bladder shape cannot be assumed to be an ellipsoid in patients with OAB. Tracing the perimeter in several 3D imaging planes better accounts for the non-uniform geometry, providing a more accurate volume measurement. Volumes estimated by VBih 2 or by tracing the bladder in 3D were not significantly different from VH2O, demonstrating that these are the most accurate methods of non-invasive assessment of bladder volume.
Funding Source(s): NIH R01DK101719, VCU Presidential Research Quest Fund, and VCU Dean’s Undergraduate Research Initiative
