Usefulness of renal volume measurements obtained by a 3-dimensional sonographic transducer with matrix electronic arrays

Objective. The purpose of this study was to examine the feasibility of 3-dimensional (3D) sonography using a matrix array transducer to measure renal volume. Methods. One hundred consecutive patients with a normal serum creatinine level and kidney appearance on computed tomography (CT) performed within 2 months before sonography were enrolled in this study. Two hundred individual renal volumes were blindly obtained by the ellipsoid formula, the stacked ellipse method, the voxel count method using routine 2-dimensional (2D) sonographic data, 3D sonographic data using a matrix array transducer, and CT data, respectively. The voxel count method was validated as the reference standard by the water displacement method in 10 cadaveric pig kidneys (r = 0.99; P < .001). Renal volumes determined by 2D and 3D sonography were compared with volumes determined by CT. Results. Volumes determined by 2D sonography were significantly lower than those determined by CT (P < .001) but similar to those determined by 3D sonography (P = .78). The percent volume error of 3D sonography (mean ± SD, -2.2% ± 3.7%) was significantly lower than that of 2D sonography (-15.7% ± 11.8%) with CT as the standard (P < .001). The correlation coefficient between 3D sonography and CT (r = 0.98; P < .0001) was better than that between 2D sonography and CT (r = 0.83; P < .0001). In addition, Bland-Altman analysis revealed that the limits of agreement between 3D sonography and CT (-9.7% to 5.1%) were narrower than those between 2D sonography and CT (-45.6% to 9.8%). Conclusions. Three-dimensional sonography with a matrix array transducer can significantly reduce renal volume measurement errors and offers a reliable means of determining renal volumes.