Estimation of Total Kidney Volume in Autosomal Dominant Polycystic Kidney Disease

Background In autosomal dominant polycystic kidney disease (ADPKD), obtaining measured total kidney volume (mTKV) by magnetic resonance (MR) imaging and manual tracing is time consuming. Two alternative MR imaging methods have recently been proposed to estimate TKV (eTKV ellipsoid and eTKV PANK ), which require less time. Study Design Cross-sectional and longitudinal diagnostic test study. Setting & Participants Patients with ADPKD with a wide range of kidney function and an approved T2-weighted MR image obtained at the University Medical Centers of Groningen, Leiden, Nijmegen, and Rotterdam, the Netherlands, in 2007 to 2014. Test set for assessing reproducibility, n=10; cohort for cross-sectional analyses, n=220; and cohort for longitudinal analyses, n=48. Index Tests Average times for eTKV ellipsoid and eTKV PANK were 5 and 15 minutes, respectively. Bias is defined as (mTKV − eTKV)/mTKV × 100%; precision, as one standard deviation of bias. Reference Tests mTKV using manual tracing to calculate the area within kidney boundaries times slice thickness. Average time for mTKV was 55 minutes. Results In the test set, intra- and intercoefficients of variation for mTKV, eTKV ellipsoid , and eTKV PANK were 1.8% and 2.3%, 3.9% and 6.3%, and 3.0% and 3.4%, respectively. In cross-sectional analysis, baseline mTKV, eTKV ellipsoid , and eTKV PANK were 1.96 (IQR, 1.28-2.82), 1.93 (IQR, 1.25-2.82), and 1.81 (IQR, 1.17-2.62) L, respectively. In cross-sectional analysis, bias was 0.02% ± 3.2%, 1.4% ± 9.2%, and 4.6% ± 7.6% for repeat mTKV, eTKV ellipsoid , and eTKV PANK , respectively. In longitudinal analysis, no significant differences were observed between percentage change in mTKV (16.7% ± 17.1%) and percentage change in eTKV ellipsoid (19.3% ± 16.1%) and eTKV PANK (17.8% ± 16.1%) over 3 years. Limitations Results for follow-up data should be interpreted with caution because of the limited number of patients. Conclusions Both methods for eTKV perform relatively well compared to mTKV and can detect change in TKV over time. Because eTKV ellipsoid requires less time than eTKV PANK , we suggest that this method may be preferable in clinical care.