The relationship between imaging features of diffusion-weighted imaging and prognosis of chronic kidney disease

Berchtold et al. reported that corticomedullary differentiation (CMD) abnormality in the apparent diffusion coefficient (ADC) for diffusion-weighted magnetic resonance (MR) imaging affords an index that is significantly correlated with prognosis in chronic kidney disease. 1 Berchtold L. Crowe L.A. Combescure C. et al. Diffusion-magnetic resonance imaging predicts decline of kidney function in chronic kidney disease and in patients with a kidney allograft. Kidney Int. 2022; 101: 804-813 Google Scholar We express our gratitude for their kind attention to our previous studies. 2 Inoue T. Kozawa E. Okada H. et al. Noninvasive evaluation of kidney hypoxia and fibrosis using magnetic resonance imaging. J Am Soc Nephrol. 2011; 22: 1429-1434 Google Scholar ,3 Sugiyama K. Inoue T. Kozawa E. et al. Reduced oxygenation but not fibrosis defined by functional magnetic resonance imaging predicts the long-term progression of chronic kidney disease. Nephrol Dial Transplant. 2020; 35: 964-970 Google Scholar The major difference between our study and that of the Berchtold’s group is the setting of the objective variable: we performed multiple regression analysis using the continuous variable, the annual rate of change in estimated glomerular filtration rate (estimated glomerular filtration rate [eGFR] slope; in ml/min per 1.73 m2 per year), as the quantitative objective variable, whereas Berchtold et al. performed Cox proportional analysis using the composite end point of a >30% decline in eGFR or initiation of renal replacement therapy as the qualitative objective variable. The loss of CMD is a feature of images, not only diffusion-weighted images, demonstrating decreased eGFR and correlates with eGFR. 4 Inoue T. Kozawa E. Ishikawa M. et al. Comparison of multiparametric magnetic resonance imaging sequences with laboratory parameters for prognosticating renal function in chronic kidney disease. Sci Rep. 2021; 11: 22129 Google Scholar Also, from conventional renal MR images, such as T1-weighted images, it is well known that the corticomedullary border is obscured in kidneys with reduced function. The Berchtold’s group reported that CMD abnormality in the ADC was a significant explanatory variable for the end point even after adjustment for eGFR; however, we think it is essential to compare it with other MR images to prove its relation to kidney fibrosis. Whether the significant association between the CMD and the end point set in their article is limited to diffusion-weighted imaging is an important issue to be examined in the future. Diffusion-magnetic resonance imaging predicts decline of kidney function in chronic kidney disease and in patients with a kidney allograftKidney InternationalVol. 101Issue 4PreviewKidney cortical interstitial fibrosis is highly predictive of kidney prognosis and is currently assessed by evaluation of a biopsy. Diffusion-weighted magnetic resonance imaging is a promising non-invasive tool to evaluate kidney fibrosis. We recently adapted diffusion-weighted imaging sequence for discrimination between the kidney cortex and medulla and found that the cortico-medullary difference in apparent diffusion coefficient (ΔADC) correlated with histological interstitial fibrosis. Here, we assessed whether ΔADC as measured with diffusion-weighted magnetic resonance imaging is predictive of kidney function decline and dialysis initiation in chronic kidney disease (CKD) and patients with a kidney allograft in a prospective study encompassing 197 patients. Full-Text PDF The authors reply:Kidney InternationalVol. 101Issue 5PreviewWe appreciate the interest of Inoue et al. in our article exploring the use of diffusion-magnetic resonance imaging to predict the decline of kidney function in chronic kidney disease and in patients with a kidney allograft.1 Full-Text PDF