Kidney Volume Estimations with Ellipsoid Equations by Magnetic Resonance Imaging in Autosomal Dominant Polycystic Kidney Disease

Abstract

Background: Kidney volume (KV) becomes clinically relevant in autosomal dominant polycystic kidney disease (ADPKD) management. KV can be conveniently estimated (ceKV) using ellipsoid volume equations with three axes measurements; however, the accuracy and reliability are unknown. Methods: KVs of 347 kidneys in 177 consecutive ADPKD patients were determined with a volumetric method (standard-KV), and ceKV was calculated using six different ellipsoid equations with three axes measurements using magnetic resonance imaging. The inter- and intraobserver reliabilities were analyzed using intraclass correlation coefficients (ICCs). Ellipsoid-KVs were obtained by linear regression analysis between standard-KV and ceKVs, and six ellipsoid-KVs were validated with a bootstrap model. Results: The ICCs of intra- and interobserver reliabilities in standard-KV and axes measurements were highly reliable. All ceKVs underestimated standard-KV and % differences between ceKV and standard-KV were reduced by ellipsoid-KVs. Bootstrap analyses suggested that six ellipsoid-KVs reliably simulated standard-KV. Conclusion: Among six ellipsoid-KVs, ellipsoid-KV₃ = 84 + 1.01 x π/24 × Length × (sum of two width measurements)² relatively accurately simulated the standard-KV. Kidney volume estimation using ellipsoid equations is reliably applied to clinical management of ADPKD while recognizing wide scattering in the difference between estimated and volumetrically measured kidney volume.

Automatic Segmentation of Kidneys using Deep Learning for Total Kidney Volume Quantification in Autosomal Dominant Polycystic Kidney Disease

“…The most commonly used methods for kidney volume computation such as manual delineation and stereology 13 are simple but time consuming and subject to intra/inter-observer variability. Alternatively, the mid-slice method 14 and the ellipsoid equation 15, 16 serve to provide quick TKV measurement but lead to low accuracy and precision compared to whole kidney segmentation.…”

“…As a consequence, several methods have been proposed with the goal of providing sufficiently accurate but less tedious means for TKV computation. The mid-slice method 14 and the ellipsoid volume equations 15, 16 have been proposed for estimating TKV from 1–2 slices. Even though these methods facilitate fast quantification, they provide only a rough estimate of TKV which could be convenient for clinical management but inadequate for clinical trials to detect smaller changes estimated to be approximately 5% 7, 10 per year.…”

A Review of the Imaging Techniques for Measuring Kidney and Cyst Volume in Establishing Autosomal Dominant Polycystic Kidney Disease Progression

“…1Ac, d) [17,36,38,39]. The 2 basic ellipsoid equations are as follows: The maximal width (W) is determined perpendicularly to L on the same slice that L is localized on.…”

“…Higashihara et al [38] showed that intra-and interobserver reproducibility of kidney dimensions and calculated renal volumes derived from MRI scans was good, with an intraclass correlation coefficient of > 0.9. However, compared with standard planimetry, the ellipsoid formulas used tended to underestimate kidney volume, with the most accurate formula being π/24 × L × (W + WW) 2 .…”

Urinary Level of Liver-Type Fatty Acid Binding Protein Reflects the Degree of Tubulointerstitial Damage in Polycystic Kidney Disease

“…To evaluate the potential use of urinary parameters as a predictor of an increased TKV, the basic ellipsoid equation, which correlates strongly with the kidney volume measured by MRI, was used to estimate the TKV in 20-(n=12) and 24-week-old (n=12) rats as described below [14]: TKV = (maximal longitudinal length × maximal width × maximal depth × π/6) of the left kidney + (maximal longitudinal length × maximal width × maximal depth × π/6) of the right kidney…”