Prognostic significance of the extent of tubulointerstitial lesions in patients with IgA nephropathy

Based on functional and histopathological correlations: is diffusion kurtosis imaging valuable for noninvasive assessment of renal damage in early-stage of chronic kidney disease?

PURPOSE

To evaluate the potential of 3 T magnetic resonance diffusion kurtosis imaging (DKI) in assessing the renal damage in early-stage of chronic kidney disease (CKD) patients with normal or slightly changed functional index, using histopathology as reference standard.

METHODS

49 CKD patients and 18 healthy volunteers were recruited in this study. CKD patients were divided into two groups based on estimated glomerular filtration rate (eGFR): Study group I (eGFR ≥ 90 ml/min/1.73 m2 [n = 20]) and Study group II (eGFR < 90 ml/min/1.73 m2 [n = 29]). DKI was performed in all participants. The DKI parameters (mean kurtosis [MK], mean diffusivity [MD], fractional anisotropy [FA]) of renal cortex and medulla were measured. The differences of parenchymal MD, MK and FA values among the different groups were compared. The correlations between DKI parameters and clinicopathological characteristics were assessed. Diagnostic performance of DKI to assess renal damage in early-stage of CKD was analyzed.

RESULTS

The cortex MD and MK showed significant difference among three groups (P < 0.05): trend of cortex MD: Study group II < Study group I < control group; trend of cortex MK: control group < Study group I < Study group II. The cortex MD and MK and medulla FA were correlated with eGFR and Interstitial fibrosis/Tubular atrophy score (0.3 < r < 0.5). Cortex MD and MK yielded an AUC of 0.752 for differentiating healthy volunteers from CKD patients with eGFR ≥ 90 ml/min/1.73 m2.

CONCLUSION

DKI shows potential in non-invasive and multi-parameter quantitative assessment of renal damage in early-stage of CKD patients and provide additional information for changes in renal function and histopathology.

Evaluating the renal mild tubulointerstitial damage and renal function in IgAN patients: a comparative study based on diffusion kurtosis imaging and diffusion tensor imaging

OBJECTIVE

To compare the performance of 3.0 T magnetic resonance diffusion kurtosis imaging (DKI) and diffusion tensor imaging (DTI) in evaluation of the degree of tubulointerstitial damage and renal function in Immunoglobulin A Nephropathy (IgAN) patients.

METHODS

Both DKI and DTI were performed in 40 IgAN patients and 17 healthy volunteers. IgAN patients were divided into two groups according to tubulointerstitial lesion score: Mild injury group, n = 24; Moderate-severe injury group, n = 16. DKI characteristic parameters [mean kurtosis (MK), axial kurtosis (Ka), radial kurtosis (Kr)] and DTI parameters [fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Da), radial diffusivity (Dr)] of renal cortex and medulla were measured and compared among different groups. Correlations between DKI, DTI parameters and clinicopathological characteristics were assessed. Diagnostic performance of DKI and DTI to evaluate tubulointerstitial damage of IgAN was compared.

RESULTS

Cortical MK, Kr, Da and parenchymal Ka significantly differed among three groups (P < 0.05). Cortical MK, Kr, Ka were negatively correlated with estimated glomerular filtration rate (eGFR) (MK: r = - 0.613; Kr: r = - 0.539; Ka: r = - 0.664) and positively correlated with tubulointerstitial lesion score (MK: r = 0.655; Kr: r = 0.577; Ka: r = 0.661) (all P < 0.001). Lower correlation coefficient was found among cortical FA, MD, Dr and eGFR, tubulointerstitial lesion score (all|r|< 0.350). The AUCs of DKI and DTI parameters for differentiating Mild injury group from control group were (cortical MK 0.822, cortical Ka 0.816; cortical FA 0.515, cortical MD 0.714) and for differentiating Mild injury group from Moderate-severe injury group were (cortical MK 0.813, cortical Ka 0.831; medulla FA 0.784, medulla MD 0.586).

CONCLUSION

Compared with DTI, DKI was more sensitive and accurate to probe the renal function and the tubulointerstitial damage of IgAN, especially the mild tubulointerstitial damage.