3DUS as an alternative to MRI for measuring renal volume in children with autosomal dominant polycystic kidney disease

Background Total kidney volume, measured by magnetic resonance imaging (MRI), is a validated disease progression marker in adults with autosomal dominant polycystic kidney disease (ADPKD). However, in childhood, MRI is burdensome, explaining the need for alternatives. Methods Kidney volume (KV) was evaluated in 30 children with ADPKD, using three-dimensional ultrasound (3DUS), applying the ellipsoid method and manual contouring (KV3DUS-ellipsoid, KV3DUS-contour respectively); manual contouring on MRI (KVMRI), and the ellipsoid method on two-dimensional ultrasound (2DUS, KV2DUS). Correlations and differences were evaluated using Pearson's r and Wilcoxon signed-rank tests, and variability using Bland-Altman plots. Results All ultrasound volumetry methods showed significantly lower mean (+/- SD) KV (mL), compared with MRI-KV2DUS: 159 (+/- 101); K3DUS-ellipsoid: 169 (+/- 105); KV3DUS-contour: 185 (+/- 110); KVMRI: 206 (+/- 130); all p < 0.001. All had a strong correlation with KVMRI: 2DUS: r = 0.96; 3DUS-ellipsoid: r = 0.89 and 3DUS-contour: r = 0.94. Both before and after correction factor application, Bland-Altman plots showed lower variability and absolute error for KV3DUS-contour vs KV2DUS and KV3DUS-ellipsoid. Conclusions Compared with MRI, ultrasound volumetry was prone to underestimation. However, KV3DUS-contour represents a valuable alternative for MRI in early ADPKD. Although more time-consuming, KV3DUS-contour is recommended over KV2DUS for estimation and follow-up of KV in ADPKD children, given its smaller error.