Comparison of 2D and 3D ultrasound methods to measure serial bladder volumes during filling: Steps toward development of non-invasive ultrasound urodynamics.

OBJECTIVES: Non-invasive methods to objectively characterize overactive bladder (OAB) and other forms of voiding dysfunction using real-time ultrasound are currently under development but require accurate and precise serial measurements of bladder volumes during filling. This study's objective was to determine the most accurate and precise ultrasound-based method of quantifying serial bladder volumes during urodynamics (UD).

METHODS: Twelve female participants with OAB completed an extended UD procedure with the addition of serial bladder ultrasound images captured once per minute. Bladder volume was measured using three ultrasound methods: (1) Vspheroid : two-dimensional (2D) method calculated assuming spheroid geometry; (2) Vbih : 2D correction method obtained by multiplying Vspheroid by a previously derived correction factor of 1.375; and (3) V3D : three-dimensional (3D) method obtained by manually tracing the bladder outline in six planes automatically reconstructed into a solid rendered volume. These volumes were compared to a control (Vcontrol ) obtained by adding UD infused volume and the volume of estimated urine production.

RESULTS: Based on linear regression analysis, both Vbih and V3D were fairly accurate estimators of Vcontrol , but V3D was more precise. Vspheroid significantly underestimated Vcontrol .

CONCLUSIONS: Although the Vbih and V3D methods were more accurate than the more-commonly used Vspheroid method for measuring bladder volumes during UD, the V3D method was the most precise and could best account for non-uniform bladder geometries. Therefore, the V3D method may represent the best tool required for the continued development of non-invasive methods to diagnose OAB and other forms of voiding dysfunction.