Total Kidney Volume Measurements in ADPKD by 3D and Ellipsoid Ultrasound in Comparison with Magnetic Resonance Imaging

Abstract

Background and Objectives: Total kidney volume (TKV) is a validated prognostic biomarker for autosomal dominant polycystic kidney disease (ADPKD). TKV by magnetic resonance imaging (MRI) and manual segmentation is considered the "reference standard", but is time-consuming and not readily accessible. By contrast, 3-dimensional ultrasound (3D ultrasound) provides a promising technology for TKV measurements with unknown potential. Here, we report a comparative study of TKV measurements by 3D ultrasound vs. the conventional methods by ultrasound ellipsoid and MRI ellipsoid. Design, setting, participants, and measurements: Single-center prospective study of 142 patients who completed a standardized 3D ultrasound and MRI. TKV by 3D ultrasound and ultrasound ellipsoid were compared to those by MRI. We assessed the agreement of TKV measurements by Bland-Altman plots and misclassification of the Mayo Clinic Imaging Classes (MCIC) between the different imaging methods, and prediction of MCIC 1C-1E by average ultrasound kidney length >16.5 cm. Results: Compared to MRI manual segmentation, MRI ellipsoid, 3D ultrasound, and ultrasound ellipsoid underestimated TKV (mean difference: -3.2%, -9.1%, and -11.0%) with MCIC misclassified in 11%, 21% and 22% of patients, respectively; most misclassified cases by MRI ellipsoid (11/16), 3D ultrasound (23/30), and ultrasound ellipsoid (26/31) were placed into a lower MCIC. Prediction of the high-risk MCIC (1C-1E) by MRI ellipsoid, 3D ultrasound, and ultrasound ellipsoid all yielded high positive predictive value (96%, 95%, 98%), and specificity (96%, 96%, 99%). However, both negative predictive value (90%, 88%, 95%) and sensitivity (88%, 85%, 94%) were lower for 3D ultrasound and ultrasound ellipsoid compared to MRI ellipsoid. An average ultrasound kidney length >16.5 cm was highly predictive of MCIC 1C-1E only in patients aged <45 years. Conclusions: TKV measurements in ADPKD by 3D ultrasound and ultrasound ellipsoid displayed similar bias, variability, and are less accurate than MRI ellipsoid. Prediction of high-risk MCIC (1C-1E) by all three methods provides high positive predictive value, but ultrasound ellipsoid is simpler to use and more readily available.

Urinary Citrate Is Associated with Kidney Outcomes in Early Polycystic Kidney Disease

“…Finally, we measured TKV on the basis of the ultrasound ellipsoid formula because computed tomography/magnetic resonance imaging data were unavailable. We recognize that underestimation of TKV using ultrasound might have occurred (18). In conclusion, low urinary citrate excretion is associated with a faster eGFR decline and worse kidney survival in patients with ADPKD, representing a potential marker of rapid disease progression.…”

“…Finally, we measured TKV on the basis of the ultrasound ellipsoid formula because computed tomography/magnetic resonance imaging data were unavailable. We recognize that underestimation of TKV using ultrasound might have occurred (18).…”

A deep learning model for CT-based kidney volume determination in dogs and normal reference definition

“…Owing to its importance in the assessment of renal function and diseases, several methods have been proposed to predict kidney volume based on diagnostic imaging. One study proposed ultrasonographic determination of kidney volume in dogs using prolate ellipsoid geometric formulae ( 7 ), but several studies have reported that measuring kidney size using ultrasound causes errors and can be inaccurate or have poor reproducibility ( 8 – 11 ). The voxel count method based on computed tomography (CT) has been reported to be an accurate method for evaluating kidney volume ( 12 – 14 ).…”

Regional variation in tolvaptan prescribing across England: national data and retrospective evaluation from an expert centre

“…The availability of newer semi-automated and automated methods for TKV measurement will make this issue irrelevant in the future [ 17 , 26 ]. In the interim, the ellipsoid equation requires only two length measurements per kidney, has reasonable performance compared with more sophisticated methods [ 27 ] and in fact was used to derive the MIC [ 16 ].…”