Evaluation of gallbladder volume and emptying with a novel three-dimensional ultrasound system: comparison with the sum-of-cylinders and the ellipsoid methods.

To overcome the geometrical limitations of current methods to calculate gallbladder volume from two-dimensional sonographic images, we evaluated the accuracy and precision of a novel three-dimensional ultrasound system (3D). In vitro accuracy of 3D volumetry (10 mL to 55 mL) was 98.1 +/- 7.1% (mean+/-SD) with a mean difference of 0.7 mL between the measured and the true volume (p < 0.003). Compared with the sum-of-cylinders (SC) and the ellipsoid (EL) methods, 3D was characterized by a significantly smaller systematic bias and closer limits of agreement with the true volume. The variation coefficient was smallest with 3D (2.4%, p < 0.02) and largest with EL (4.2%). In vivo, gallbladder volumes were on average 1.4 mL (9%) smaller with 3D than with SC (p < 0.0001) and 2.4 mL (14%) larger with EL than with SC (p < 0.0001). 3D ultrasonography accurately measures gallbladder volume and emptying.