Our study results indicate a correlation between T1 values and various pathological scores, as well as the occurrence of adverse renal events. Elevated cortical T1 values in CKD patients correlate with a poorer prognosis and an increased likelihood of adverse renal events. This suggests that native T1 mapping might serve as a noninvasive biomarker for evaluating fibrosis and predicting prognosis in CKD patients.
While studies have highlighted the potential of native T1 mapping to assess CKD patients in kidney disease research, findings have consistently shown that T1 values in CKD patients are significantly longer than those in control groups [11]. Our prior study with chronic glomerulonephritis patients yielded similar results [7]. Additionally, native T1 mapping has been suggested to have a pivotal role in evaluating renal function impairment in transplant recipients and IgA nephropathy patients [12, 13]. In our current research, we found notable differences in kidney T1 values between healthy control groups and CKD G1-4 patients, further cementing the strong relationship between kidney T1 values and renal function.
CKD covers a spectrum of etiologies, advancing through shared pathological mechanisms such as glomerular capillary hypertension and hyperfiltration, inflammation, vascular rarefaction, hypoxia, and fibrosis [14, 15]. Increasing evidence suggests MRI techniques hold immense promise in evaluating and quantifying kidney disease’s pathophysiological processes. Functional MRI can assess renal tissue perfusion, oxygenation, interstitial diffusion, cellular metabolism, and molecular expression with techniques like diffusion weighted imaging(DWI), diffusion tensor imaging(DTI), blood oxygen level development(BOLD), and magnetic resonance elastography(MRE) [16,17,18,19]. Additionally, recent research underscores the potential of T1 mapping in assessing renal fibrosis. Preliminary research has shown that T1 mapping effectively gauges renal fibrosis in mice with CKD [20]. Friedli et al. [21] discovered that T1 values correlate well with fibrosis and inflammation, offering an evaluation metric for transplanted kidneys’ interstitial fibrosis. Graham-Brown et al. [13] reported rising T1 values in patients with high interstitial damage scores. Our biopsy analysis of 63 patients revealed that T1 values align with fibrosis scores, reflecting fibrosis levels. Our preceding study also corroborated these findings. Nevertheless, more extensive multicenter studies are essential to validate T1 mapping. Currently, there’s a dearth of longitudinal studies that delve into functional MRI’s predictive value in assessing renal function alterations and prognosis. Some studies using BOLD to assess renal oxygenation have shown correlations with declining renal function, validating the chronic hypoxia hypothesis, and paving the way for future research [22].
In our study involving 119 CKD patients, we determined that T1 value might be an independent risk factor for CKD prognosis. Cox regression analysis, focusing on adverse kidney events, revealed correlations with age, diabetes, baseline eGFR, 24-h urinary protein, T1 value, CysC, Hb, and endpoint events. Subsequent multivariate analysis suggested that, after accounting for confounding factors, 24-h urine protein, CysC, Hb, and T1 were independent risk factors. Past research has shown anemia accelerates kidney function decline and ups end stage renal diseases incidence rates [23, 24]. 24-h urine protein is also a significant risk factor for CKD onset [25], while CysC indicates kidney filtration function and can flag early declines in kidney function [26]. Our ROC curve analysis determined that CysC, with an AUC value of 0.83, was the strongest determinant for adverse kidney events, followed by T1 (AUC = 0.77) and Hb (AUC = 0.73). But combining these indicators pushed the AUC value to 0.88, amplifying the predictive capability for adverse kidney events.
We would like to observe whether there is a specific group, within which the prognosis of the kidneys is worse. In our study, T1 values ranged from 1600 to 2000. We attempted to group patients reasonably for the first time. Eventually, patients with T1 values exceeding 90% of the highest value in the cohort were classified into the high T1 group, while those with values below 90% of the highest value in the cohort were categorized into the low T1 group. Grouping T1 values showed that the high T1 group had over thrice the likelihood of adverse events than the low T1 group. With the most extended follow-up spanning 38 months, the two CKD groups showed significant differences over time in terms of the absence of adverse kidney events, boosting T1 mapping’s potential to predict CKD prognosis.
This study, however, had some limitations. First, it’s a single-center, retrospective cohort study. Even after accounting for multiple factors, confounding variables persist, with potential confounders overlooked due to the retrospective nature. Second, no patients who underwent renal biopsy had more than 50% renal IF. Third, this study only focused on CKD; more research is required to investigate the clinical value of T1 mapping in other renal diseases. Last but not least, researches on the utility of T1 mapping compared to other modalities and its correlation with markers of tubular injury are still lacking. Future research will expand the cohort, add more markers and redo MRI scans on the previous subjects to affirm the prognostic value of T1 mapping for CKD patients.
In conclusion, native T1-mapping not only evaluates the kidney function of CKD patients but also mirrors their prognosis. It holds promise as a novel non-invasive method for predicting adverse kidney events in CKD patients.
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- Source: https://bmcnephrol.biomedcentral.com/articles/10.1186/s12882-024-03559-1