Detecting Early Kidney Allograft Fibrosis with Multi-b-value Spectral Diffusion MRI

TL;DR

This study demonstrates that spectral diffusion MRI can detect early and mild kidney allograft fibrosis, potentially allowing for earlier intervention before functional decline occurs.

Contribution

It introduces the use of multi-b-value spectral diffusion MRI for early detection of kidney allograft fibrosis, showing promising diagnostic accuracy.

Findings

Spectral diffusion MRI detected fibrosis with AUC=0.72 in patients with stable eGFR.

It identified mild/moderate fibrosis with AUC=0.65, comparable to ADC.

The method detected fibrosis before decline in kidney function.

Abstract

Kidney allograft fibrosis is a marker of chronic kidney disease (CKD) and predicts functional decline, and eventual allograft failure. This study evaluates if spectral diffusion MRI can help detect early development and mild/moderate fibrosis in kidney allografts. In a prospective two-center study of kidney allografts, interstitial fibrosis and tubular atrophy (IFTA) was scored and eGFR was calculated from serum creatinine. Multi-b-value DWI (bvalues=[0,10,30,50,80,120,200,400,800mm2/s]) was post-processed with spectral diffusion, intravoxel incoherent motion (IVIM), and apparent diffusion coefficient (ADC). Connection between imaging parameters and biological processes was measured by Mann-Whitney U-test and Spearman's rank; diagnostic ability was measured by five-fold cross-validation univariate and multi-variate logistic regression. Quality control analyses included volunteer MRI (n=4) and inter-observer analysis (n=19). 99 patients were included (50$\pm$13yo, 64M/35F, 39 IFTA=0, 22 IFTA=2, 20 IFTA=4, 18 IFTA=6, 46 eGFR<=45mL/min/1.73m2, mean eGFR=47.5$\pm$21.3mL/min/1.73m2). Spectral diffusion detected fibrosis (IFTA>0) in patients with normal/stable eGFR>45ml/min/1.73m2 [AUC(95$\%$CI)=0.72(0.56,0.87),p=0.007]. Spectral diffusion detected mild/moderate fibrosis (IFTA=2-4) [AUC(95$\%$CI)=0.65(0.52,0.71),p=0.023], as did ADC [AUC(95$\%$CI)=0.71(0.54,0.87),p=0.013)]. eGFR, time-from-transplant, and allograft size could not. Interobserver correlation was >0.50 in 24 out of 40 diffusion parameters. Spectral diffusion MRI showed detection of mild/moderate fibrosis and fibrosis before decline in function. It is a promising method to detect early development of fibrosis and CKD before progression.