Objective: To determine the reproducibility of three-dimensional (3D) ultrasonography (US) using a matrix array transducer (3D US-MAT) as a means of measuring renal volume and to investigate correlations between renal volume and renal function.
Methods: Institutional review board approval was obtained, and all patients gave informed consent. One hundred-twenty patients, comprised of 20 consecutive patients with each of the five stages of chronic renal disease and 20 normal volunteers (stage 0), were enrolled in this study. Individual renal volumes were determined using the ellipsoid formula from two-dimensional (2D US) data, and using the stacked ellipse method from 3D US-MAT data by two independent observers. Volume measurement reproducibilities were evaluated for both of these methods. After normalizing total renal volumes (TRV), correlations between normalized TRVs (nTRVs) determined using both methods and estimated glomerular filtration rates (eGFR) were evaluated. Differences between nTRVs at each stage of chronic renal disease were also evaluated.
Results: The reproducibility of 3D US-MAT was greater than that of 2D US, and the correlation coefficient between nTRVs by 3D US-MAT and eGFRs for two observers (r=0.809 and 0.813; p<0.001) was better than that between nTRVs by 2D US and eGFRs (r=0.696 and 0.715; p<0.001). Mean nTRVs in both stage 0 and 1 were significantly greater than those in other stages (p<0.001), and Mean nTRV of stage 5 was significantly lower than those in other stages ( p<0.001).
Conclusions: 3D US-MAT offers a reliable means of measuring renal volumes during evaluations of patient with reduced renal function.