Accuracy and processing time of kidney volume measurement methods in rodent polycystic kidney disease models: superiority of semi-automated kidney segmentation.

Measurement of total kidney volume (TKV) using magnetic resonance imaging (MRI) is a valuable approach for monitoring disease progression in autosomal dominant polycystic kidney disease (ADPKD) and is becoming more common in preclinical studies using animal models. Manual contouring of kidney MRI areas (i.e., manual method (MM)) is a conventional, but time-consuming, way to determine TKV. We developed a template-based semi-automatic image segmentation method (SAM) and validated it in three commonly used PKD models, Cys1cpk/cpk mice, Pkd1RC/RC mice, and Pkhd1pck/pck rats (n=10 per model). We compared SAM-based TKV with those obtained by clinical alternatives including the ellipsoid formula-based method (EM) using three kidney dimensions, the longest kidney length method (LM), and the MM, which is considered the gold standard. Both SAM and EM presented high accuracy in TKV assessment in Cys1cpk/cpk mice (interclass correlation coefficient (ICC)≥0.94). SAM was superior to EM and LM in Pkd1RC/RC mice (ICC=0.87, 0.74, and <0.10 for SAM, EM, and LM, respectively) and Pkhd1pck/pck rats (ICC=0.59, <0.10, and <0.10, respectively). Also, SAM outperformed EM in processing time in Cys1cpk/cpk (3.6±0.6 vs 4.4±0.7 minutes per kidney)and Pkd1RC/RC mice (3.1±0.4 vs 7.1±2.6 minutes) (both p<0.001), but not in Pkhd1PCK/PCK rats (3.7±0.8 vs3.2±0.5 minutes). LM was the fastest (~1 min), but correlated most poorly with MM-based TKV in all studied models. Processing times by MM were longer for Cys1cpk/cpk mice, Pkd1RC/RC mice, and Pkhd1pck.pck rats (66.1±7.3, 38.3±7.5, and 29.2±3.5 minutes). In summary, SAM is a fast and accurate method to determine TKV in mouse and rat PKD models.