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.