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

Pedram Akbari; Fatemeh Nasri; Shirley Deng; Saima Khowaja; Seung Lee; William Warnica; Hua Lu; Anand Rattansingh; Mostafa Atri; Korosh Khalili; York Pei

doi:10.2215/CJN.14931121

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.

Received November 16, 2021.
Revision received March 9, 2022.
Accepted March 22, 2022.

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